Having bought a 'Power Monkey' solar charging device, I was very impressed by the simplicity and quality of the products I'd picked up thus far. This small UV Indicator was recommended as an item I might have interest in, so I gave in and bought it; more out of the very low price, than considering exactly what usage I'd get from it.
The item's simple enough (what can go wrong with zero moving parts?), with an 'indicator' material mounted on a small plastic disc, and with a small loop that should allow it to be attached (and therefore not lost) easily.
Taking it out of the packaging was about the most impressive moment, as trying to get any sort of reaction from the disc didn't appear to make any difference, even when I has this on the dashboard of my car, in brilliantly sunny summer weather (it does happen occassionally!), there was only the very faintest of change in the disc.
From that point, I basically gave up on the idea of it being of any particular use; for it to slide from car to a drawer, then a drawer to the bin.
For the money, it wasn't even worth writting a letter and asking for a refund. Simply best avoided.