There is a Firefly buily for the iPhone 😉
http://www.tuaw.com/2007/10/31/stream-music-from-your-iphone-to-itunes-with-firefly-media-serve/
And I can confirm, its working quite nice 😀
I dont know if there is a pocketpc port, but it might compile on other Linux based embedded devices (PDA/Phones).