I stumbled across this interesting SourceForge project. Bemused is a system which allows you to control your music collection from your phone, using Bluetooth. It requires a Series 60 or UIQ phone (e.g. Nokia 7650/3650, or Sony Ericsson P800), and a PC with a Bluetooth adapter.

So apparently I can control Winamp from my P900. The only thing left to do is buy a bluetooth dongle for the PC.