Back Hair Mower

You roll this palm-sized doohickey along on your back. It looks just like one of those plastic back massagers with the three balls that feels all weird when you rub your skin with it.

But it has wheels, and as you push it, they turn a sharp lawnmower blade (don't worry; it's inset, for your safety.) This blade will cut any rogue footlongs down to a more evolution theory-supporting 1/4 inch length. It's easy and it's fun! No batteries required.

[This is another of my friend Caroline's ideas. Isn't she creative?]

Edit: Please don't give these to friends as gag gifts. It's not meant to be funny, just useful.