From the vaults at ThinkGeek: "Each Sonic Screwdriver feels just perfect. It doesn't really do all the cool things in the series (just in case the Cybermen are able to buy them), but it does have lights and sounds straight from the show - and it extends too! One end has a purple UV light and the other has a pen nib. You can use the regular pen nib to write shopping lists and the UV ink pen nib to write secret plans. These can then be revealed with the UV light of the Sonic Screwdriver. Equip up, Junior Time Lords - it's time to go Dalek hunting."
Funny, there appears to be no actual screwdriver. (I'd buy it anyway.)