This is not quite related, but since people interested in astronomy are likely to read this thread: on the iphone of a friend, I saw a planetarium application. You hold the phone above your head and it shows the name of the stars behind the phone. It uses the built-in gps and time to compute the local sky and the built-in accelerometers and compass to compute "what the phone is looking at". It works a bit like the Celestron skyscout.
That would be great to have on the N900.