A good rear light is an essential, but many riders avoid using one, since it's easily stolen. The Danish-designed KiBiSi iFlash One bike light fixes the problem. It comes in two parts: a plastic attachment that clasps onto handlebars, stems, or the seat post, and the light itself, which affixes to the attachment via a strong magnet that also acts as an on switch. At ride's end, it's easy to pop the iFlash off. It casts a capable glow and works for 60 hours per charge. [$25; iflash.dk]