One device plugs into the sound card, the other plugs into the stereo. An IR remote control is included. Line in on stereo. IrMan is one of the more videly available commercial devices. Also available as kit.
Some TV cards comes with remote control.
Combined with the right software, all these devices will allow you to control ex. WinAmp from a regular IR remote control. So if you have a PC in the room, wired to a decent set of speakers, this could be a very cost effective solution. You can buy UIR on-line from Rathronics . To make it easy, the following class definitions have been used to clasify the different types of devices presented here.