On an ORD-NRT flight once, I looked out the window and was stunned to discover I was flying directly over FAI, a town in which I had once lived. I was able to get a text message of greeting off to an old friend there telling him to look up.

I don't do it often, but on occasion, I've tried to get a signal. It's very difficult and often requires holding the phone up to the window--it seems anywhere else results in the signal being attenuated too much (perhaps the aircraft skin itself acts as a Faraday cage).