We covered Signal
when it first dropped in the middle of last year, and now Alloysoft has sent us a note that they've upgraded to version 1.1. The app turns your iPhone into an iTunes remote through a server connection, so you don't need to jailbreak or hack the phone at all -- just run the program on your Mac, and you can use your iPhone as a replacement for the Apple Remote. And Signal actually works in Windows as well, so you can use it to control WMP, or even use a Windows Mobile device as a control instead. No idea why you'd torment yourself with Windows Media, but that's your row to hoe.
Version 1.1 brings control for AirTunes, so now you can switch speakers directly from the iPhone, and there's a host of new features -- Webclip support, an Alphabetic library, and Landscape support. Nice little program that's available as a free demo
or as a registered version for $24.95