Easy-Macro is a super simple macro lens for cell phones that performs quite well. At $14.95, it's a decent price, too. This was a Christmas present from Ryan and I can't wait for Spring to come around so I can get lots of insect and flower macros. Keep it in your pocket or your purse so you can always have the option to get real close to your photography subject.
This is what it looks like when put on my iPhone 5s. I usually have it over my case, though which keeps it extra snug and there's no chance of it falling off.
And, here are some images I've captured with my phone using this lens: