Physics Toolbox Suite.

Most phones today contain a powerful array of sensors, and almost all of them are locked from easy access by the user. Physics Toolbox has functions that allow you to get the raw data from almost every sensor in your phone. It’s the only “tool” app that I can honestly say I’ve used as a tool. It has a sound intensity functions which I have used to determine if hearing protections is needed, and I’ve used that feature to diag a bad mic pickup due to an ambient white noise machine. It can give you the signal loss for a WiFi connection, very handy for troubleshooitng wireless access points.

Other features, magnetic field detection, tone generator, color matcher, g-force and rotation output, raw GPS view and more. All of these are available on the free version, but I actually use this app so much that I spent the 2 or 5 bucks to the dev mainly just to support them. The laid version also lets you export the sensor logs to a .csv file so you can view that data on a computer.

It really turns your phone from a glorified Lemmy portal into the cool future tool it was meant to be.