UV Monkey is a little keychain UV index tester which warns when the nasty part of sunlight is getting dangerous to your skin and health. The more purple it becomes the higher the ultraviolet exposure, the more cover up you need. Around $6.50.
The UV Monkey is a tiny detector that will keep track of the level of evilness from the UV rays that are bursting through the athmosphere. Just expose The UV Monkey to sunlight and it will, instandly, tell you how strong the devious rays are at that exact moment.