PowerTutor is an application for Google phones that displays the power consumed by major system components such as CPU, network interface, display, and GPS receiver and different applications. The application allows software developers to see the impact of design changes on power efficiency. Application users can also use it to determine how their actions are impacting battery life. PowerTutor uses a power consumption model built by direct measurements during careful control of device power management states. This model generally provides power consumption estimates within 5% of actual values. A configurable display for power consumption history is provided. It also provides users with a text-file based output containing detailed results. You can use PowerTutor to monitor the power consumption of any application.
PowerTutor's power model was built on HTC G1, HTC G2 and Nexus one. It will run on other versions of the GPhone, but when used with phones other than the above phone models, power consumption estimates will be rough. We plan to provide power models for other phones in the future.
More info about PowerTutor can be found here.