I am imagining the creation of such a device; it seems to be a tricky one. most compasses work on a needle-like object being able to float in the direction of the earth's magnetic field. So to make something like that which can be used internal to the body and provide feedback about where it is; seems difficult.

I have been wearing a magnetic ring for several weeks and plan to write about my experiences, but essentially it would also not do what you want it to do.

North paw is the only thing I can think of. I can suggest more wearable devices but they require you to access them. I wonder if you could wear something near your ear that could somehow hint at which way it was facing (possibly with sound) or something in your mouth. Part of the problem is that we don't have a lot of methods of finding magnetic north. its basically just using needles or magnets.