This page ought to document the current state of iPhone on Linux development (that is, syncing iPhones and iPod Touches with Linux, not running Linux on them!). I’ll get to it sometime.

For now, there’s a usbmuxd subpage. Usbmuxd is the lowest level component, in charge of talking to the actual device over USB and letting other applications talk to the phone. I used to be the maintainer of this bit.