Hi I am designing a project I have a pcb with a plastic enclosure I also have a perminant magnet in the enclosure. I want the device to go into deep sleep when the device is stuck to a metal object and then wake up when it is removed. I have two ideas but I'm wondering if anyone has a better idea. My first idea is to have a compass ic near the magnet and detect the change in the magnetic field when it is stuck to something. My second idea is to have the magnet free to move slightly and constrained by a small spring. Then have the pcb have a capacitive pickup like that for touch sensors. When the magnet is stuck to something the pickup will change capacitance. Does anyone have better ideas than these two?