[Hcgilje] threw together a tutorial on using serial communications in iPhone applications. It builds upon the DevDot tutorial which was posted back in 2007. A lot has changed since then; the firmware has come a long way and there are several development tools that now make things a bit easier for you. His examples use Interface Builder and openFrameworks to demonstrate GUI control of an LED and a servo motor. Now go out and design your own peripherals for this popular handset.