diff --git a/callback-manager/.clang-format b/callback-manager/.clang-format
new file mode 100644
index 0000000..ea71ad6
--- /dev/null
+++ b/callback-manager/.clang-format
@@ -0,0 +1,99 @@
+---
+Language:        Cpp
+# BasedOnStyle:  LLVM
+AccessModifierOffset: -2
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignEscapedNewlinesLeft: false
+AlignOperands:   true
+AlignTrailingComments: true
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: None
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+AlwaysBreakAfterDefinitionReturnType: None
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: true
+BinPackArguments: true
+BinPackParameters: true
+BraceWrapping:
+  AfterClass:      true
+  AfterControlStatement: true
+  AfterEnum:       true
+  AfterFunction:   true
+  AfterNamespace:  true
+  AfterObjCDeclaration: true
+  AfterStruct:     true
+  AfterUnion:      true
+  BeforeCatch:     true
+  BeforeElse:      true
+  IndentBraces:    false
+BreakBeforeBinaryOperators: None
+BreakBeforeBraces: Custom
+BreakBeforeTernaryOperators: true
+BreakConstructorInitializers: AfterColon
+ColumnLimit:     80
+CommentPragmas:  '^ IWYU pragma:'
+ConstructorInitializerAllOnOneLineOrOnePerLine: false
+ConstructorInitializerIndentWidth: 4
+ContinuationIndentWidth: 4
+Cpp11BracedListStyle: true
+DerivePointerAlignment: false
+PointerAlignment: Left
+DisableFormat:   false
+ExperimentalAutoDetectBinPacking: false
+FixNamespaceComments: true
+ForEachMacros:   [ foreach, Q_FOREACH, BOOST_FOREACH ]
+IncludeBlocks: Regroup
+IncludeCategories:
+  - Regex:           '^[<"](gtest|gmock)'
+    Priority:        5
+  - Regex:           '^"config.h"'
+    Priority:        -1
+  - Regex:           '^".*\.hpp"'
+    Priority:        1
+  - Regex:           '^<.*\.h>'
+    Priority:        2
+  - Regex:           '^<.*'
+    Priority:        3
+  - Regex:           '.*'
+    Priority:        4
+IndentCaseLabels: true
+IndentWidth:     4
+IndentWrappedFunctionNames: true
+KeepEmptyLinesAtTheStartOfBlocks: true
+MacroBlockBegin: ''
+MacroBlockEnd:   ''
+MaxEmptyLinesToKeep: 1
+NamespaceIndentation: None
+ObjCBlockIndentWidth: 2
+ObjCSpaceAfterProperty: false
+ObjCSpaceBeforeProtocolList: true
+PenaltyBreakBeforeFirstCallParameter: 19
+PenaltyBreakComment: 300
+PenaltyBreakFirstLessLess: 120
+PenaltyBreakString: 1000
+PenaltyExcessCharacter: 1000000
+PenaltyReturnTypeOnItsOwnLine: 60
+ReflowComments:  true
+SortIncludes:    true
+SortUsingDeclarations: true
+SpaceAfterCStyleCast: false
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: ControlStatements
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 1
+SpacesInAngles:  false
+SpacesInContainerLiterals: true
+SpacesInCStyleCastParentheses: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+Standard:        Cpp11
+TabWidth:        4
+UseTab:          Never
+...
+
diff --git a/callback-manager/.gitignore b/callback-manager/.gitignore
new file mode 100644
index 0000000..0cb1d79
--- /dev/null
+++ b/callback-manager/.gitignore
@@ -0,0 +1,3 @@
+build/*
+oe-logs
+oe-workdir
diff --git a/callback-manager/CMakeLists.txt b/callback-manager/CMakeLists.txt
new file mode 100644
index 0000000..80a3dcc
--- /dev/null
+++ b/callback-manager/CMakeLists.txt
@@ -0,0 +1,74 @@
+cmake_minimum_required (VERSION 3.1 FATAL_ERROR)
+set (BUILD_SHARED_LIBRARIES OFF)
+include (ExternalProject)
+set (CMAKE_CXX_STANDARD 17)
+set (CMAKE_CXX_STANDARD_REQUIRED ON)
+set (CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake ${CMAKE_MODULE_PATH})
+set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-rtti")
+set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fno-rtti")
+
+option (YOCTO "Enable Building in Yocto" OFF)
+
+if (NOT YOCTO)
+    externalproject_add (
+        Boost URL
+        https://dl.bintray.com/boostorg/release/1.66.0/source/boost_1_66_0.tar.gz
+        URL_MD5 d275cd85b00022313c171f602db59fc5 SOURCE_DIR
+        "${CMAKE_BINARY_DIR}/boost-src" BINARY_DIR
+        "${CMAKE_BINARY_DIR}/boost-build" CONFIGURE_COMMAND "" BUILD_COMMAND ""
+        INSTALL_COMMAND mkdir -p "${CMAKE_BINARY_DIR}/prefix/include/" && cp -R
+        ${CMAKE_BINARY_DIR}/boost-src/boost ${CMAKE_BINARY_DIR}/prefix/include
+    ) # requires apt install autoconf-archive and autoconf
+    externalproject_add (sdbusplus-project PREFIX
+                         ${CMAKE_BINARY_DIR}/sdbusplus-project GIT_REPOSITORY
+                         https://github.com/openbmc/sdbusplus.git GIT_TAG
+                         bed15f0cee4784acdf151cca14efdfb98cb9d397 SOURCE_DIR
+                         ${CMAKE_BINARY_DIR}/sdbusplus-src BINARY_DIR
+                         ${CMAKE_BINARY_DIR}/sdbusplus-build CONFIGURE_COMMAND
+                         "" BUILD_COMMAND cd ${CMAKE_BINARY_DIR}/sdbusplus-src
+                         && ./bootstrap.sh && ./configure --enable-transaction
+                         && make -j libsdbusplus.la INSTALL_COMMAND ""
+                         LOG_DOWNLOAD ON)
+
+    include_directories (${CMAKE_BINARY_DIR}/sdbusplus-src)
+    include_directories (${CMAKE_BINARY_DIR}/nlohmann/include)
+    include_directories (${CMAKE_BINARY_DIR}/nlohmann/include/nlohmann)
+    include_directories (${CMAKE_BINARY_DIR}/phosphor-dbus-interfaces/include)
+    link_directories (${CMAKE_BINARY_DIR}/sdbusplus-src/.libs)
+
+    include_directories (${CMAKE_BINARY_DIR}/boost-src)
+    set (CMAKE_PREFIX_PATH ${CMAKE_BINARY_DIR}/boost-src ${CMAKE_PREFIX_PATH})
+    option (ENABLE_TEST "Enable Google Test" OFF)
+    if (ENABLE_TEST)
+        hunter_add_package (GTest)
+        find_package (GTest CONFIG REQUIRED)
+        enable_testing ()
+    endif ()
+endif ()
+
+add_definitions (-DBOOST_ERROR_CODE_HEADER_ONLY)
+add_definitions (-DBOOST_SYSTEM_NO_DEPRECATED)
+add_definitions (-DBOOST_ALL_NO_LIB)
+add_definitions (-DBOOST_NO_RTTI)
+add_definitions (-DBOOST_NO_TYPEID)
+add_definitions (-DBOOST_ASIO_DISABLE_THREADS)
+
+include_directories (${CMAKE_CURRENT_SOURCE_DIR}/include)
+include_directories (${Boost_INCLUDE_DIRS})
+include_directories (${CMAKE_CURRENT_SOURCE_DIR}/include)
+
+add_executable (callback-manager src/callback_manager.cpp)
+
+target_link_libraries (callback-manager -lsystemd)
+target_link_libraries (callback-manager stdc++fs)
+target_link_libraries (callback-manager ${Boost_LIBRARIES})
+target_link_libraries (callback-manager sdbusplus)
+
+if (NOT YOCTO)
+    add_dependencies (callback-manager sdbusplus-project)
+endif ()
+
+set (SERVICE_FILES ${PROJECT_SOURCE_DIR}/service_files/callback-manager.service)
+
+install (TARGETS callback-manager DESTINATION sbin)
+install (FILES ${SERVICE_FILES} DESTINATION /lib/systemd/system/)
diff --git a/callback-manager/LICENCE b/callback-manager/LICENCE
new file mode 100644
index 0000000..729f4d4
--- /dev/null
+++ b/callback-manager/LICENCE
@@ -0,0 +1,13 @@
+Copyright 2019 Intel Corporation
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
diff --git a/callback-manager/cmake-format.json b/callback-manager/cmake-format.json
new file mode 100644
index 0000000..4a68fb7
--- /dev/null
+++ b/callback-manager/cmake-format.json
@@ -0,0 +1,13 @@
+{
+  "enum_char": ".",
+  "line_ending": "unix",
+  "bullet_char": "*",
+  "max_subargs_per_line": 99,
+  "command_case": "lower",
+  "tab_size": 4,
+  "line_width": 80,
+  "separate_fn_name_with_space": true,
+  "dangle_parens": true,
+  "separate_ctrl_name_with_space": true
+}
+
diff --git a/callback-manager/service_files/callback-manager.service b/callback-manager/service_files/callback-manager.service
new file mode 100644
index 0000000..b6abae3
--- /dev/null
+++ b/callback-manager/service_files/callback-manager.service
@@ -0,0 +1,13 @@
+[Unit]
+Description=Callback Manager
+StopWhenUnneeded=false
+
+[Service]
+Type=dbus
+BusName=xyz.openbmc_project.CallbackManager
+Restart=always
+RestartSec=5
+ExecStart=/usr/sbin/callback-manager
+
+[Install]
+WantedBy=multi-user.target
diff --git a/callback-manager/src/callback_manager.cpp b/callback-manager/src/callback_manager.cpp
new file mode 100644
index 0000000..706c607
--- /dev/null
+++ b/callback-manager/src/callback_manager.cpp
@@ -0,0 +1,202 @@
+/*
+// Copyright (c) 2019 Intel Corporation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+*/
+
+#include <boost/container/flat_map.hpp>
+#include <iostream>
+#include <sdbusplus/asio/connection.hpp>
+#include <sdbusplus/asio/object_server.hpp>
+#include <variant>
+
+constexpr const char* fatalLedPath =
+    "/xyz/openbmc_project/led/groups/status_critical";
+constexpr const char* criticalLedPath =
+    "/xyz/openbmc_project/led/groups/status_non_critical";
+constexpr const char* warningLedPath =
+    "/xyz/openbmc_project/led/groups/status_degraded";
+
+constexpr const char* ledIface = "xyz.openbmc_project.Led.Group";
+constexpr const char* ledAssertProp = "Asserted";
+constexpr const char* ledManagerBusname =
+    "xyz.openbmc_project.LED.GroupManager";
+
+std::shared_ptr<sdbusplus::asio::dbus_interface> assertedIface = nullptr;
+
+constexpr const bool debug = false;
+
+// final led state tracking
+bool fatalState = false;
+bool criticalState = false;
+bool warnState = false;
+
+// maps of <object-path, <property, asserted>>
+boost::container::flat_map<std::string,
+                           boost::container::flat_map<std::string, bool>>
+    fatalAssertMap;
+boost::container::flat_map<std::string,
+                           boost::container::flat_map<std::string, bool>>
+    criticalAssertMap;
+boost::container::flat_map<std::string,
+                           boost::container::flat_map<std::string, bool>>
+    warningAssertMap;
+
+std::vector<std::string> assertedInMap(
+    const boost::container::flat_map<
+        std::string, boost::container::flat_map<std::string, bool>>& map)
+{
+    std::vector<std::string> ret;
+    // if any of the properties are true, return true
+    for (const auto& pair : map)
+    {
+        for (const auto& item : pair.second)
+        {
+            if (item.second)
+            {
+                ret.push_back(pair.first);
+            }
+        }
+    }
+    return ret;
+}
+
+void updateLedStatus(std::shared_ptr<sdbusplus::asio::connection>& conn)
+{
+    std::vector<std::pair<std::string, std::variant<bool>>> ledsToSet;
+
+    std::vector<std::string> assertedVector = assertedInMap(fatalAssertMap);
+    assertedIface->set_property("Fatal", assertedVector);
+
+    bool fatal = assertedVector.size();
+    if (fatal != fatalState)
+    {
+        fatalState = fatal;
+        ledsToSet.push_back(std::make_pair(fatalLedPath, fatalState));
+    }
+
+    assertedVector = assertedInMap(criticalAssertMap);
+    assertedIface->set_property("Critical", assertedVector);
+
+    bool critical = assertedVector.size();
+    if (critical != criticalState)
+    {
+        criticalState = critical;
+        ledsToSet.push_back(std::make_pair(criticalLedPath, criticalState));
+    }
+
+    assertedVector = assertedInMap(warningAssertMap);
+    assertedIface->set_property("Warning", assertedVector);
+
+    bool warn = assertedVector.size();
+    if (warn != warnState)
+    {
+        warnState = warn;
+        ledsToSet.push_back(std::make_pair(warningLedPath, warnState));
+    }
+
+    for (const auto& ledPair : ledsToSet)
+    {
+        conn->async_method_call(
+            [ledPair](const boost::system::error_code ec) {
+                if (ec)
+                {
+                    std::cerr << "Cannot set " << ledPair.first << " to "
+                              << std::boolalpha
+                              << std::get<bool>(ledPair.second) << "\n";
+                }
+                if constexpr (debug)
+                {
+                    std::cerr << "Set " << ledPair.first << " to "
+                              << std::boolalpha
+                              << std::get<bool>(ledPair.second) << "\n";
+                }
+            },
+            ledManagerBusname, ledPair.first, "org.freedesktop.DBus.Properties",
+            "Set", ledIface, ledAssertProp, ledPair.second);
+    }
+}
+
+void createThresholdMatch(std::shared_ptr<sdbusplus::asio::connection>& conn)
+{
+    static std::unique_ptr<sdbusplus::bus::match::match> match = nullptr;
+
+    std::function<void(sdbusplus::message::message&)> thresholdCallback =
+        [&conn](sdbusplus::message::message& message) {
+            std::string objectName;
+            boost::container::flat_map<std::string, std::variant<bool>> values;
+            message.read(objectName, values);
+
+            if constexpr (debug)
+            {
+                std::cerr << "Threshold callback " << message.get_path()
+                          << "\n";
+            }
+
+            auto findCriticalLow = values.find("CriticalAlarmLow");
+            auto findCriticalHigh = values.find("CriticalAlarmHigh");
+
+            auto findWarnLow = values.find("WarningAlarmLow");
+            auto findWarnHigh = values.find("WarningAlarmHigh");
+
+            if (findCriticalLow != values.end())
+            {
+                criticalAssertMap[message.get_path()]["Low"] =
+                    std::get<bool>(findCriticalLow->second);
+            }
+            if (findCriticalHigh != values.end())
+            {
+                criticalAssertMap[message.get_path()]["High"] =
+                    std::get<bool>(findCriticalHigh->second);
+            }
+            if (findWarnLow != values.end())
+            {
+                warningAssertMap[message.get_path()]["Low"] =
+                    std::get<bool>(findWarnLow->second);
+            }
+            if (findWarnHigh != values.end())
+            {
+                warningAssertMap[message.get_path()]["High"] =
+                    std::get<bool>(findWarnHigh->second);
+            }
+            updateLedStatus(conn);
+        };
+
+    match = std::make_unique<sdbusplus::bus::match::match>(
+        static_cast<sdbusplus::bus::bus&>(*conn),
+        "type='signal',interface='org.freedesktop.DBus.Properties',path_"
+        "namespace='/xyz/openbmc_project/"
+        "sensors',arg0namespace='xyz.openbmc_project.Sensor.Threshold'",
+        thresholdCallback);
+}
+
+int main(int argc, char** argv)
+{
+    boost::asio::io_service io;
+    auto conn = std::make_shared<sdbusplus::asio::connection>(io);
+    conn->request_name("xyz.openbmc_project.CallbackManager");
+    sdbusplus::asio::object_server objServer(conn);
+    assertedIface =
+        objServer.add_interface("/xyz/openbmc_project/CallbackManager",
+                                "xyz.openbmc_project.CallbackManager");
+    assertedIface->register_property("Warning", std::vector<std::string>());
+    assertedIface->register_property("Critical", std::vector<std::string>());
+    assertedIface->register_property("Fatal", std::vector<std::string>());
+    assertedIface->initialize();
+
+    createThresholdMatch(conn);
+
+    io.run();
+
+    return 0;
+}