I just got a new phone, so I'm letting my 4 year old play with my old one. He was fairly amused with the different games and things... but then I showed him how to take pictures, and he loves it! So far he's taken pictures of the cat, my hands, the light, the t.v., army guys, police cars and the cat mess (which was caused by him looking at the phones screen while walking).
It's so super awesome to watch him walk around and try to find cool things to photograph.
Except he keeps trying to take pictures of me, and that sucks, since I'm still sitting around in my Radioshack uniform.