Not only do Gizmon’s Clip-On Lenses offer a smart and speedy way to mount them on your iPhone, but they also break with the now-common fisheye-telephoto-wideangle triumvirate (mostly at least), instead coming in fisheye, polarizer and "3-image mirage filter" flavors. Better still, they will also play just fine with your iPad 2 or 3.
The lenses simply clip over the corner of your iDevice, and the clip is just the right length to put the glass over the camera lens (one clip is enough as the lenses actually screw into it). The fisheye ($35) speaks for itself, and these can be a lot of fun to play with. The 3-image mirage ($25) filter looks interesting too, although it’s doubtful you’d use it more than a few times after seeing the novelty image-splitting effect.
Best is the circular polarizer ($25). The polarizer, which cuts out or lets in polarized light depending on how you turn it, is the only photographic filter which can’t be applied in post using software. It will make blue skies bluer, cut the reflections from glass or water and generally make sunlit scenes more saturated. It also acts somewhat as a neutral-density filter, cutting out light which can help bring down exposures on bright days.
I’m a happy user of the magnetic lenses I have from Photojojo, but they are a real pain to mount on the iPad. This clip-on version looks so good that I might have to fashion a clip mount myself. Available now.