[voidUpdate]

From my limited knowledge, itwould be very hard to make it react to all types of radiation (alpha, beta, gamma) since they penetrate differently and interact with forces differently. You could potentially make a magnetic "lens" that would interact with alpha and beta particles, but gamma rays would ignore it.

The best way I can think of to make a "radiation camera" is similar to how you can make a "wifi camera", by hooking up a radiation detector to a pan-tilt mechanism, and moving it around very slowly and sampling the amount of radiation detected at each point. Essentially a single pixel "camera" that you have to move around to take a full picture. However, you'd also have to shield the detector from any radioactivity coming from directions that it's not pointed in, which is especially hard if you're trying to capture gamma rays, since they like to penetrate through everything. Its like if light could leak into the side of a normal camera, you'd get rubbish photos

[dmurray]

Why would it have to be a single pixel instead of an array of sensors like any digital camera?

Sure, we probably can't make Geiger counters in a form factor that allows an array of a million of them in a handheld device, but maybe 20x16 or something?

[voidUpdate]

I mean you could make that work, but you'd have to shield between all of the detectors so that you don't get the radiation equivalent of bloom on your pictures. If you have only one, it'll be easier to shield, in my head anyway