All sorts of shit. If my phone is on silent, and my mom calls me twice, then it'll switch to rumble on the second call. It'll switch to full sound on the third - because obviously the call is urgent. Right? Right mom? You didn't call me three times in a row to tell me to wear my boots, right?
I actually think I stole that from Klein.
When I plug my phone into a wall, it's screen dims, wifi and 3g turn off, and the screen turns off faster. Features return when I unplug.
When I'm on my way home, I have a button I can press that let's my sis (who is usually messaging me) know that I'm mid-commute.
Then, when my phone detects my apartment wifi, she get's a message that I'm back home and can begin messaging me again. I also narrowed this down to only work on specific days and times.
A fun one is to just change my phone's ringtone with every new call.
The OH SHIT alarm - if my phone is face down, and the screen is off, 30 minutes before class starts, trigger an alarm. There is a 95% chance that I have been oversleeping and am about to pay the iron price.
When I'm not on home wifi, have my passlock enabled. When I'm at home, leave it unlocked.