DACP is used to control an iTunes server from a remote device. No audio is passed, just control messages. It is the primary protocol used by the iOS Remote application.

I think that this would / will make an excellent webOS application. Should be able to sell for about £5. I would expect to sell about 1,000 minimum.

DAAP & DACP Docs

Also iTunesControl which uses Python etc & works under OS-X.