OhGizmo's Andrew Liszewski took the Phlash Universal Cameraphone Flash for a spin, using it to add flash capabilities to his Motorola RAZR. He says it works as promised, illuminating a meter outwards so you can do things like photograph your NES in a dark room (what he did, before and after above) or drunkenly take photos of your equally drunk friends in a dimly-lit bar (what we'd do, in theory).
At $29.99 it's still very pricey for what is after all just an LED stuck to the back of your camera. If you think this is something you'd use a lot, then by all means spend for it. If not, you might want to considering getting a small LED keychain light instead—we keep an Inova Microlight with our keys in case of emergencies, and it only set us back $6.50.