I've never heard of Deezer - I'll have to check them out.And Spotify's rival Deezer.
My understanding is that Deezer allows for full integration through Bluetooth too.
I use spotify as I get a free Premium subscription with my mobile contract, otherwise I'd choose Deezer as I think they are the same price.
(Incidentally I found out the free ad-supported version of Spotify doesn't allow for full integration, as you can only shuffle play your playlists not select a track from them.)
JustPark also integrates with the Nav system, to provide info on local parking spaces.
Glympse integrates and offers something but I can't figure out what it is!! Journey tracking and sharing, but only the last 10 miles or so of your journey (??)