Simplify Media, makers of an application that allows friends to stream each others' music collections over the internet from right within iTunes, has a new trick up their sleeve: an alpha app for the iPhone and iPhone Touch that allows you to listen to your home iTunes music collection any time you're near an open WiFi connection. You can also use it to listen to the music in up to 30 of your friends' music libraries, so long as they have iTunes running and Simplify Media's iTunes or Winamp plug-in installed.
In order for this to work, you'd need to jailbreak your iPhone and install AppTap, which "comes with absolutely no warranty of any kind." You'd also need to have Apple's iPhone firmware version 1.1.1 or 1.1.2 installed. (According to Simplify, one of the big advantages of its approach is that the music playing application doesn't tie up Safari the way its competitors' web-based approaches do.)
Why Apple didn't include this functionality to begin with is anyone's guess.
Here's avideo demo of an iPhone streaming an iTunes library over WiF:
http://www.youtube.com/watch?v=W0qxs-P6NFQ
