Unfortunately smart phone cameras kinda suck performance wise. Radiation detectors fundamentally need some mass to actually absorb and detect radiation, so while cameras are basically similar to semiconductor radiation detectors the performance is so bad as to be useless. I haven't really ever seen the camera detectors be used for anything useful.

Radiacode detectors are about the only affordable detector with actually useful performance out there, and they are around $300. Which is also drastically cheaper than anything else out there, the next cheapest actually useful detector out there that I know of is 10x that price.