There are dozens of strap-on fisheye lenses that you can buy nowadays for iPhones. Blame it on Lomography and Hipstamatic, perhaps. Pixeet's goes a step further though, letting you shoot full 360-degree panoramas with the camera lens and free app.
It works by taking four photos with the iPhone's camera, which are then stitched together with the app, creating that 360-degree panorama which your Facebook profile has (probably not) been crying out for. You can see several examples of the panoramas created, here.