Recently my iPhone was stolen. The first thing the thief did was to turn off the device, entirely eliminating the ability to trace the phone through MobileMe.
What I'm interested in is an app, well more of a "tweak" that would essentially remove the power slider functionality of the power button when the iPhone is @ the lock screen and has a passcode lock enabled.
Essentially, from a locked screen, one would press power to wake the phone up (pressing power will wake/sleep the phone while passcode locked, but holding it will not show the power off slider at this point) followed by entering their passcode. Once at the home screen holding power will show the power off slider as normal.
This functionality would go a long way in securing the ability to trace recently stolen phones.