I have a Samsung Infuse running Android 2.2. I'd like the screen to lock, with a PIN, but ONLY after a certain amount of idle time (e.g. 15 minutes). In other words, I want to be able to turn the display on and off with a few minutes in between without the phone locking at all, but if I leave the display off for 15 minutes and try to turn it back on, it will require a PIN to do so. Is there an app for that???