I have an idea for an iPhone game that I'd like to prove out first without diving in to an Intel mac, iPhone and dev license. The concept should be demonstrable through the browser, but it's a kind of head-to-head game where some content comes to and from a content server, but the logic would all be between two players fighting each other on different machines. Graphics wouldn't be too fancy.

Can anyone recommend an SDK or set of technology to do this? Most of my experience is with web app development using Rails, Sinatra, Django, etc. I'm thinking that the client-side logic and graphics would be more suited to something like Flash or Silverlight or whether I could actually pull this off with a ton of javascript. But, I don't know about network communications between two instances. Any tips or leads?