Show HN: Smartphone Magnetic Field Visualizer (vieyrasoftware.net)

Used the digital compass in my phone the other day to set various lab magnetic stirrers to the same rotational velocity using a app that plotted the reading from the sensor over time. Incredible what the average smartphone is equipped to do.

LOL I do not envy the weird emails you are going to get from psychotics and ghost-hunters around this thing..