The fact that iPhone web apps can't access iPhone hardware comes up all the time here. It seems odd to me that nobody mentions the fact that, with not much work, it's possible to create an iPhone browser that can give a website access to
most of the iPhone hardware through javascript: gps/location services, the camera, the photo library, the music library, the accelerometer, and so on. One enterprising developer wrote an iPhone browser that does just that. here it is:
http://www.big5apps.com/I can't really recommend that app, though. Most of it is open source, so you can go see for yourself that the code is terrible. The app is ugly, leaks abound, and so on. The guy really doesn't know objective-c. I became aware of it because I have a contracting client that wanted to use that app, discovered it was terrible, and paid me to write a better one.
I think this is an idea that is ripe for the picking, but I can't see how, really. I have most of such a browser written. Who can think of a way to monetize this?