The Concerts App ( http://nxtbgthng.com/concerts ), my London MusicHackDay Project, gets remote Spotify integration: When you are on an artists page, you can browse the albums and tracks on Spotify, and make it play the track remotely on the desktop via WiFi!

There is also a little iPhone Application called "SpotifyRemote" that lets you search for an artist, browse his stuff and play it on the desktop. It uses the same code than the Concerts app and serves as a demo and test case. It can also write emails and open the MusicHackDay site - remotely.

For achieving all this, there is a Desktop Daemon, that announces itself via "Bonjour" and takes URLs that it will open in the system. This Demon can be shared between different iPhone/iPad or Mac Clients, it can be used for multiple purposes, and in the future it will have a plugin system and a backchannel for communicating information from the desktop to the client. It will, when it's no longer a hack, be opensourced and available to be shared by (hopefully) a lot of mobile Apps.