[HTCotta]

The light sensor isn't actually what shuts the phone off when you put it to your ear to talk, it's a proximity sensor. I don't think there's a way to have it auto lock the phone but PocketShield will lock when you press the power button to shut off the screen and unlock via the light sensor when you press it again to wake it up. So if it wakes in your pocket it stays locked, but outside where there is light, auto unlock. It's a paid program but it's worth every penny.