There's 2 of them. The Cycloramic and the Cycloramic Pro. One is 99 cents and the other one is $1.99. You can get it in the app store.
Printable View
Here is a video that shows it in action. You need a flat smooth surface. It is cool, but I don't know how often I would use it. Android phones have been able to do 360 panoramics for a while (not hands free) and I never use it.
http://www.youtube.com/watch?v=7jFGvZjovZk