Android Device Monitor is a stand-alone tool that provides a graphical user interface for several Android application debugging and analysis tools. The Monitor tool does not require installation of an integrated development environment, such as Eclipse, and encapsulates the following tools:
To start Device Monitor, enter the following command from the SDK
Start an Android emulator or connect an Android device via USB cable, and connect Device Monitor to the device by selecting it in the Devices window.
Note: Only one debugger can be connected to your device at a time. If you're using ADT, you may need to close the debugging tool before launching the Device Monitor in order for the device to be fully debuggable.