Best way (if possible) to have a Broadcast between iphones

[nicodio]

Hi, I'm quite new to Iphone programming and I don't know if what I want to do is possible. I didn't find a lot of informations on the web so I'm asking you:

I have to do a project for university where an Iphone have to send and receive message to/from other iphone in its range without being connected to a LAN (it would be an adaptation of a VANET [veicular ad-hoc network] with iphones).
Is that possibile?

In that case can I use wi-fi or only bluetooth?
I read about Bonjour but it can only used inside a LAN (is it right?), what about Game Kit Framework?

Thank you