So... here are a few ideas:
- Use the built-in (crude) GPS on the iPhone to geo-tag your sky images. Unfortunately, the iPhone's camera is terrible, but one can imagine using it the position to show you the sky about in GoogleSky (web).
- Galaxy Classification (ala GalaxyZoo), but using your iPhone
- OPO's content on an iPhone that is location aware
- VO Data, extending Mike Fitzpatrick's work (which I think is absolutely GREAT, more on this later).