Here’s how to capture a screenshot of various mobile devices while they are running:
Press-and-hold the home button then while still holding the home button down press-and-release the sleep button. The screen will flash white and you’ll hear a snapshot sound. Tested on iPhone 3GS and iPad v1.
Only solution is with a connected computer. Use the Android SDK softwware while the device is attached to your computer. http://www.addictivetips.com/mobile/how-to-take-screenshots-of-android-device. Tested on Google Nexus One.
Press the Volume Up and Volume Down buttons at the same time.