If your hobbies include using a soldering iron and spending time exploring the great outdoors, then the North Paw Directional Anklet Kit from ThinkGeek may be of interest. It's a self-build vibrating compass which straps to the ankle, allowing the user to always tell which direction magnetic north lies.
As its name suggests, the North Paw Directional Anklet Kit comes in kit form, so it’s first necessary to break out the wire strippers and soldering iron to put the device together – a process which is reported to be “easy-ish.”
Once assembled, the unit sports a total of eight vibrating pager motors, which surround your leg. Whichever direction magnetic north happens to be, the integrated compass will cause the corresponding motor to vibrate, thus allowing you to navigate hands-free.
The North Paw runs off an internal battery, which is recharged with a USB mini-B cable, and it's secured to the ankle with a Velcro strap.
While we can't vouch for its efficacy, always knowing the direction of magnetic north could certainly prove useful – just be sure not to wear it through airport security.
The North Paw Directional Anklet Kit is available from Think Geek and will set you back US$159.99.
The promo video below features an intrepid explorer demonstrating the device in use.