This is the Adonit Snap. It's an inexpensive Stylus for use on an existing touch screen device. For $40 is seemed like a good bargain at first. It worked on my iPhone 6 Plus, my Samsung Galaxy S7 and my Dell Venue 8 7000 (yes I bought one of those). It's got a nice button for turning it on and off that can be used as a camera button when paired via bluetooth. The accuracy was fine although it is far from like writing with pen and paper (or like using an Apple Pencil or Surface pen).
As far as usability, it comes with a little metal sticker that you can attach to your phone case so the magnetic Snap will attach to it like a little baby, clinging to its mother. Like that baby, it doesn't really hold that tightly so in your pocket or bag, don't expect it to stay attached. Because of this, I don't carry around as much as I thought I would because I often loose it in my pocket or it flies off while I'm taking things out of my pocket. One perk it with my replacement (see below) I received a 2nd sticker and not I use the Snap to hold my two phone together in my pocket (its just more comfortable with out them banging around in there).
In general the Snap was good for what I was looking for; a way to jot notes and using my device for reviewing math with my daughter without using a ton of paper.
Then it stopped working. It wouldn't charge. The little green light would not turn green ever again. I tried multiple chargers and cables, nothing. It was within a month so support grilled me like I was a hotdog and finally agreed to replace the device. A month later after we had swapped shipping boxes, my new Adonit Snap worked as well as the old ... including the 3rd or 4th time I went to charge it, it would not charge. This time I need to send a video to support to prove that I wasn't Silence of The Lamb'ing these poor little Snaps. The latest replacement it working for now. Cross your fingers.