While there are plenty of apps that let you stream music on the go, not many of them are particularly social. Soundtracker is different in that it’s designed from the ground up to let you discover the music that other people are listening to, and a new update released for the iPhone version of the app is out today.

Available for iPhone, Windows Phone 7, Symbian (via the Nokia Ovi Store) and Samsung Bada, at first glance this app is similar to Last.fm or Pandora. You enter an artist name, and it starts playing a themed radio station of related music by that artist and similar ones. It’s all well and good, but not exactly original. However, once you dig into the social side of things, it gets a bit more interesting.

By connecting your Twitter and Facebook accounts, you can find friends using the service and access their saved stations too. This is a neat way of curating your taste for others to discover, and an in-app messaging service too lets you get in touch with others directly to congratulate them on their taste (or just tell them that your taste is better).

Location-based discovery is also available. Near me, for example, there’s a Nina Kraviz fan and someone who has created a radio station based around Iranian music. I may not be particularly keen on these songs, but as a serendipitous way of discovering new music, it definitely has its charms. Foursquare integration is built in too, so you can check in to locations with details of the song you’re listening to, along with Facebook and Twitter sharing.

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New features in the latest update to the iPhone version of the app include suggested stations pulled in from your phone’s music library and a map view for browsing nearby stations, improved sharing options and a range of UI tweaks. The app also now carries Apple iAds.

Although it makes most sense as a mobile app, a basic browser-based version is available too.

The social features of Soundtracker certainly add an extra dimension of discovery to the app, and whilst I won’t be dropping Spotify or Last.fm on my phone for this, it certainly offers a fresh way to discover the music tastes of your friends and people nearby.