[car]

A network of scintillators in every phone would be amazing for finding stuff like this.

That was my first thought too. Do you think it’s physically possible to make a MEMS scintiallation device?

[astrange]

If you're going to put increasingly obscure health sensors in your phone, I think air quality would come before radiation.

[MengerSponge]

No. MEMS means electromechanical, and scintillation needs solid state: a crystal and a photon detector of some kind. The crystal can't be miniaturized because there's a minimum thickness you need to capture the photon and Compton electrons*.

[car]

You're right, I stand corrected.

This page [0] has an image of a small scintillator plus photomultiplier, but probably too thick for a phone.

[0]https://scan-electronics.com/en/dosimeters/radiacode-101

[qwezxcrty]

Although some weird Japanese phone makers did have smartphones with radiation detector built-in (SHARP 107sh and 205sh), I don't think it would be a popular feature.

There isn't so many cases in daily life that one can encounter a radioactive source. Even if you are actively looking for one (don't do it), you will have a hard time if you don't work with radioactive sources occupationally.

Also, it's not physically possible to create a small and yet sensitive radiation detector.

[pfdietz]

There are radiation detection apps for cell phones that use the camera. Not very sensitive, but no new hardware is required.