Meet the Magnetic Imaging Tile: a cool piece that uses an array of 64 hall effect sensors to visualize magnetic fields. It uses an analog to digital converter in addition to a magnetic sensor. The Magnetic Imaging Tile is able to detect roughly +/- 0.5mT per bit.
As SparkFun’s people explain:
For our demo in the gif we used a SAMD21 Mini to clock out the ADC data to the serial port at 115200. The serial is then parsed by a Processing sketch. All software is open source and available in the repo. This setup can achieve over 76 frames per second. With buffering the setup is capable of 200 fps. The ChipKit MAX32 is also supported and can achieve around 2,000fps. A faster processor should be able to achieve 1500fps