TPE (as previously mentioned) does the sunrise/sunset thing, but cleverly takes into account your altitude and will show you that say a hill in front of you will block the sun, and specify the time the sun will breach that hill.
Now that is cool! Amazing where technology is taking us
Perhaps we'ld better start an Android thread too eh? I bought a Point of View Mobii (same thing as Advent Vega, ViewSonic 10s and so on) last month, not as good as the iPad but at half the price it certainly is value for money.