2 Ideas inspired from this week's new scientist
One of the reader's questions at the end of the magazine mentioned a blind kitten which had developed extra long whiskers. Whilst you cannot draw conclusions from a sample size of one there has been a study showing that there is a strong link between visual ability and facial vibrissae length (whiskers) and I'll link the full study below.
Cats use their whiskers as an extension of their touch sensitivity and I think this study shows just how important the sense is to them.
Anyway, this gave me an idea. Our body and facial hair is extremely sensitive to touch as well so what if we simply coated these hairs with a ferrous spray or paint?
I'm not sure how sensitive it would be for weak fields but for strong fields I could imagine it giving us a far more detailed though less vibrant sense than a finger magnet. It would be like the difference between a pigment spot and an optic cup giving us full 360 degree magnetic vision!
2. Transdermal GPS.
A GPS belt has been developed which buzzes on the left or right indicating when and where to turn as well as sending coded buzzes to tell them how far they traveled etc. Researchers found that users were fare more attentive than those who used normal a screen GPS.
There is a lot of hardware space to play with around the waist and GPS devices these days can run on very low power. The whole device could probably run on an average of 50mw tops.