Each pen has a built-in ultraviolet LED light, you can read messages that are invisible to the naked eye. It’s perfect for writing down personal information like your PIN number or passwords – assuming of course that nobody else has a black light lying around, and you can actually remember where the heck you wrote your note. Keep in mind that while the ink is “invisible”, it’s also permanent, so don’t be writing nasty bathroom stall limericks on the walls of your house unless you plan on living with them in perpetuity.

If you want to exchange secret notes with a friend, buy a couple and play a game to see if you can find all the hidden messages you leave for each other. Of course, running around with a UV light in hand, you might come across other evidence of foul play you didn’t intend to. Don’t mind that blood spatter – it’s nothing.

The Invisible Ink Spy Pen is available over at Perpetual Kid for $9.99 (USD).

Available for about $64 from wholesale importer ChinaVasion, the Hidden Camera Spy Clock has a full color camera that transmits to a remote receiver for recording whatever it spies.

Supposedly this thing is designed for security purposes, but I have a feeling that it’s more likely to be the source of the next Paris Hilton sex tape.