I´ve done some tests and it seems that html5 in conjunction with box2d is to slow for the iPhone. So I´ve to do it the traditional way.

But for gaining attention it would be nice to have a browser version of the game. Keep in mind: It must have pvp functionality (one vs. one over the internet).
Which brings me to the next question: Client side or server side programming? PHP or HTML5 / Flash / Unity Web Player?

I begin to think that there are too much possibilities.
The bigger the choice, the harder it is to choose.