of owls and batteries
Speaking of things that you should take out of your pocket
before scuba diving, I would also add your Owl Wallet Light to the list. The Owl Wallet Light is a credit-card-sized magnifying glass with a small light.
It's a neat idea with a relatively poor implementation. You can't see very much through the magnifying glass and you have to carefully hold it at the right angle and distance to see anything, so it's a bit tedious to try to read anything as large as a restaurant menu.
Part of the visibility problem is caused by the fact that the Owl uses a Fresnel lens. A Fresnel lens doesn't have varying thickness like a normal lens; instead it uses many small ridges to focus light. The ridges make it very hard to clean that side of the lens and the lens tends to get foggy when rubbing up against the sides of a leather wallet.
Another issue with the Owl is that the light is not bright enough in the dim lights of your typical cloth-napkin restaurant (I think cloth napkins are disgusting, by the way), but there is a new version out that has brighter lights.
Still another issue is that the Owl is disposable. There is no way to replace the batteries once they go out. Or is there? In the Owl that went scuba diving with me, the front of the card was coming up. I peeled it back and found what look like two stock hearing-aid cells underneath. It looks like you could replace them with a bit of effort. You would have to find some way to loosen the front of the card without destroying the circuitry.
My Owl is so rusted inside that it is not worth trying, but if anyone else wants to send me one with a dead battery, I'd like to give it a try. Anyone?