Whether you're still rocking an old bookshelf stereo system or a newer model with fancy speakers, this hack will give your smartphone complete control over it. Who needs a Nexus Q, anyway?
PC486, the guy behind this project, wanted to use his Android phone to control his roomate's stereo and stream the music he had on his phone without drilling holes. The solution was to take Logitech's Bluetooth audio receiver and hack it to also act as an IR remote for the stereo. At the link below, he explains all of the steps and outlines the gear you need to do the same thing.
You'll need some patience and a soldering iron for this project, but the end result lets you turn any stereo system that uses an IR remote control into a speaker you can control with your smartphone.