Building on work developed by Matthias Ringwald, who has put together a user space bluetooth stack, Ackerman has built external adapters that plug into the iPhone’s connector port, accessing the phone’s bluetooth stack in a way that could possibly even comply with the standard iPhone SDK, according to developer/blogger Erica Sadun.
With such capability developers could theoretically build games and utilities that allow phones to transfer data without having to be on the same WiFi network or connect to a server as an intermediary. Users could transfer photos, play chess against each other, shoot over a vcard, and more, using software that could be sold on App Store.
While the iPhone ships with Bluetooth capabilities, they are a limited subset of its normal features. You cannot, for example, connect your Mac to your iPhone and transfer data files.
Don’t hold your breath for Apple to take Ackerman’s lead in this arena, but this, as Sadun notes, is pretty big news and a great step forward for the effort to make iPhones communicate directly with each other.