You can get an iPhone or iPod touch and install the free "Remote" application. This will let you control iTunes on the computer to which the phone/touch is synched. Of course, the computer must already be turned on with iTunes running. But the app is cool--all controls and coverflow right in your hand and since it's using your home's wireless net, you don't have to worry about line of sight.
Home Audio Network
I have a breathaudio home system - it uses IR receivers in wall. Also have the wireless home network up and running. I can stream music [iTunes] to the home stereo and therefore throughout the house. Problem is I have to be at the computer to start music playing which is not great if you are upstairs. Question, any product out there that will allow control of the streaming music library via a remote [IR would be nice] - it could be an external hard drive, digital music receiver, etc... Sonos isn't 100% iTunes compatible.