Cool they measure using a modified android phone's sensor!Wish Faraday lived to see these field lines for real just once!How about devices that measure and use

Cool they measure using a modified android phone's sensor!Wish Faraday lived to see these field lines for real just once!How about devices that measure and use this field data to identify objects in real time to build a map around one?I don't think ill be the first one to think of this but has someone else done this before?