While I was attending the Copa America soccer game in Philadelphia last month, with the great folks at Sprint, one of the Sprint team members pulled me off to the side and put a little felt bag in my hand and said, "here you go." Well I was busy and didn't even look at what I was given and stuffed the little sack in my pocket. I month later, and I find the little bag and finally open it up.
The contents end up being two smartphone camera lenses, one a clip-on fisheye and the other an attachable lens and they work great! Thanks Sprint and glad I didn't lose this thoughtful gift.
There are a few companies that make these tiny, but useful lenses at prices ranging from about $7 to $70. Might be worth a look if you like experimenting with you smartphone camera.