Floating compasses are a great little DIY tool, but they generally need something hard to hold water, like a small dish or bowl. This innovative method uses a small, petri dish-sized duct tape bowl instead. Because the bowl's made out of duct tape, it can be rolled up with the other materials and easily fit inside a pocket or small bag.
A floating compass works by suspending a magnetised needle over water, floating it on a small piece of cork. The low weight of the cork, combined with the low resistance of the water, allows the needle to find North by just slowly spinning until it settles. Check out the link below for more images and instructions.
Duct Tape Compass [Instructables]