These lenses can be found on eBay for a few bucks. I've got mine at Mercado Livre (BR) for R$50,00 (which is like US$20).
They have a decent quality and go fine with the new Moto G. They produce some chromatic aberration, and they surely will bump your ISO up - so be careful with indoor shots, as they will be probably noisier than without the lens.
But it's not something that will compromise your selfies or daily snaps.
As for videos, my Moto G struggles in focusing. Idk why. But it almost renders videos unusable with the infinite being almost always out of focus.
The kit includes two lenses (one being splittable) and a clip. You just screw the lens to the clip, and clip it (oh really) to the phone.
It fits well in the Moto G.
Here's the fisheye. It provides a damn big angle of view.
The cool thing is that these clip lenses are versatile. You can put it in the front camera, to add some extra bam to your selfies
(in case anyone wants, here's a photo in the same distance and without the lens)
We have the Macro + Wide lenses. Split it, and it becomes a macro. Join them, and you've got a wide angle.
Here's the macro in action.
And a photo of the wide angle. (definetely not my favourite lens)
Well, they're worth it. Just be careful because sometimes the clip can leave marks on your colorful shell.