I bought a tiny plastic little glow-in-the-dark cylinder about an inch long, attaches to my key ring, useful for finding keys in the dark. Doesn't need charging up in light (it contains a wee bit of mildly radioactive gas which causes fluoresence of the pigments. Not gonna give anyone cancer!). The packet said it was guaranteed for 10 years....I bought it in 2010. Still works, best £10 I ever spent for worth.