I never bothered with a device because we have the actual sun for free, and the potential for misuse is enormous -- it's trivial to accidentally blind yourself.
Thanks. I was thinking of mounting a light onder my table, so the skin in the legs can pick up the UV-B, thereby reducing safety risks and also distraction. It would be interesting to see if a day of programming could give me the same benefits in terms of well-being as a day surfing waves :)