According to AppleInsider, it looks like Apple may be looking into turning the iPhone into a walkie-talkie device, much like the Motorola’s on the Nextel/Sprint technology. This filing was done in November of last year (2009), so is it possible that it will be in a future update of the iPhone (since we have no confirmation that it will be upgraded in June)? It also looks like they have plan to turn those unheard instant audio messages into voicemails, so if you missed it on the instant, you can go back and play it again. So far, this looks like an iPhone only feature, as AT&T does already feature Push-to-Talk
via [AppleInsider]