Lock your phone when snatched. An updated and improved derivative of PluckLock.
This polls the accelerometer in the background and will lock the phone if the sum of all non-gravitational forces ever exceeds the threshold.
PluckLockEx loads immediately into its preferences page, where you can set the only preference relevant to the app's operation: the threshold at which the phone will lock when it receives an acceleration jolt. The application will run in the background, constantly monitoring the accelerometer to determine if the phone has been taken from your hand. The app will start itself when you boot your phone.