Holy. Cow. Do I ever need some rest. I just spent most of last night figuring out how to get Bonjour (aka mDNS) running on my iPhone. Bonjour offers configuration-free networking technology. Computers (and iPhones) automagically broadcast their services, which you can then listen for and take advantage of. This has been a long-term project that I've been plugging away at for months.
So what makes this exciting? With Bonjour, your iPhone and touch can talk to your Mac. They can talk to printers or to each other. They can browse for available services or provide their own as a server. What I put together was a pair of applications: PicSend and PicListen. These apps allow you to subscribe to a camera on another person's iPhone. Just tell that iPhone to snap a picture and within seconds that picture appears on your own screen.
Link: Bonjour and the iPhone