For some inexplicable reason, picking iPhone compatible accessories always turns into an hours long process of comparing reviews. I've been wanting a fish eye lens for my phone for the longest time and finally bit the bullet recently.
I couldn't be happier with this clip on lens. It's really convenient since it can be used for both the front and back camera. I have the iPhone 6s Plus, and it fits without any issues on each side. The clip itself is a sturdy plastic material with a rubber ball on the end so it won't scratch your phone/case.
The lens I purchased actually comes with a wide angle and macro lens, so it's a great deal, although I only use the fish eye lens myself. The biggest reason for why I picked this lens kit is that it doesn't generate the blacked out round corners that seem to be common in a lot of the other fish eye lenses I came across, when positioned properly.
Here's a sample photo taken with the lens. You can see the black rounded edges at the top corners, meaning I didn't have the lens properly positioned over the iPhone camera. P.S. This kit would make a great Christmas gift if you have some last minute holiday shopping to do! Free 2 day shipping with Prime since it's an Amazon item.
Do you use camera accessories for your iPhone?