Does anyone have an idea on cost efficient water pressure/level measurement in 1000 ft deep groundwater wells? There is a new law in California that made these measurements mandatory and my good friends have to drive some crazy mileage to do manual cord measurements of water level.
Non-invasive current measurement with HMC5883L is as good as mosquito killing by the hammer - can be done but an overkill! 
Non-invasive current measurements are greatly done with wire clamp/loops.
HMC5883L is highly sensitive and low noise digital compass. It can be used in drones, smartphones, VR sets - any applications that needs to know change of physical object orientation in 3D space.
We use it for vehicle detection sensor. Did a benchmark on RMS on temperature stability with half a dozen of other sensors, ST, NXP, Bosch. HMC is the best!