I recently read 'Life on the Edge' by Jim Al-Khalili and Johnjoe McFadden. They present a case that birds' navigation involves a quantum mechanical mechanism and probably occurs somewhere in the eye.
This got me wondering about what it might be like to see the effects of the Earth's magnetic field, so I decided to tinker with the idea.
I have two starting points - the first is hacking some active 3D glasses to cause variations in some way to the users vision. The second is to add some coloured LEDs in the wearers peripheral vision, and have the colours change in some way according to the detected magnetic field.