For those who have hacked their iPhone, Erica Sudun has put together another little gem of an app called Listen, that lets your iPhone identify songs that it hears playing on your radio, on the TV, or where ever.

Listen is in beta, and the version I’m using is “beta 06” which has a nicer push-button interface than initial releases, and some more useful functionality. Because it’s beta, I should say use it at your own risk—but that pretty much goes for any app you’ve installed on your hacked iPhone or iPod touch.

If you haven’t hacked your iPhone yet, directions to help you can be found here. You can download the Listen app from the Multimedia section of the iPhone Installer app, simply listed as “Listen”. After you do so, it’s going to be listen in your Springboard home screen with a purple icon. To start it, just tap on the icon.

Once in the app, make sure you have some music is playing, from whatever source you have, so long as you can hear it and you can put your iPhone’s mic near it. Now, just tap on the big button and Listen will record a sample of the song. Shortly there after, Listen will do its thing and go out to server to compare the sample to a known database that it uses to identify the track.

Within about 30 seconds, you should have a listing of the track’s information, including the track name, artist, and album. New in this version of Listen is the ability to send that information to whoever you’d like in an email.

It’s a clever use of the iPhone’s capabilities and a great display of what independent developers can do on this amazing platform. Never again to you have to go on listening to the radio, not knowing who sings a specific song. Also, if you hear a song on you love the radio but don’t yet have it in your library, you can email the track info to yourself as a reminder to pick it up the next time you connect (or search for it in the Mobile iTunes Store if you’re on WiFi).

Check out the Listen app now and help give Erica some feedback to make it an even better app.