Rdio, the music streaming service from Skype/Kazaa founders Janus Friis and Niklas Zennstrom, has launched an iPhone app, despite still being in very private stealth beta.

The description on the app store reads: "Rdio is like carrying a giant MP3 player in your pocket – you have unlimited and unrestricted access to all the music, and you get to select exactly the song, album or artist you want to hear.

"And you can skip, pause fast forward as much as you want. Build your collection and compose your playlists on rdio.com and listen to them all on the go. Or search for just the right song when you’re out and it will start playing instantly".

The app is free to download, and from the description it sounds like it could well be troubling the likes of Spotify and Napster in 2010. We'll bring you more when we hear it.