The built-in music player on the iPhone/touch doesn’t look for “Shared Libraries” (via the DAAP protocol) like the iTunes desktop app does. Hopefully that’s something Apple will add in the near future. If/when that ever happens, our devices should be able to stream from a sharing iTunes or Firefly or whatever. Maybe someone will write a homebrew app for jailbroken devices in the meantime. Or maybe when Apple releases their developer SDK next year someone will get working on it.
There are quite a few strategies to access your music though, all of which involve running a webserver on the computer, then you connect to that from MobileSafari on the iPhone/touch. So it’s certainly possible… it really comes down to how nicely the webpage is displayed, and if it’s pages are customized for MobileSafari on the iPhone/touch display.
telekinesis – iPhone remote is one, as mentioned above.
Here are other “homebrew” tips, activating it yourself via Web sharing:
The free SlimServer has an iPhone/touch skin on the way that’s looking great.
There is also the (now) free dotTunes, along with it’s free artwork plugin. But to get the iPhone or iPod touch-friendly skin, you’ve got to shell out $20 for one of the plug-ins.
Wired blog article about it:
Those last two are probably the slickest current solutions for iPhoners.
Here are more, similar solutions:
http://tversity.com/home/ (Windows only)
http://www.simplifymedia.com/download.html (Cross Platform)
http://www.mediamaster.com/ (Cross platform)
…but I’m not sure how well their output displays on an iPhone/touch.