Not Nickel-63 - Beta particles don’t go very far in air, and are shielded by almost anything. You’ll be unlikely to be alarming on beta emitters anywhere, unless they’re right up against your specialized Beta detector.

My understanding is, the danger with Beta emitters is if they are broken up into dust, and you breathe the dust in (or eat/drink it) then you are toast, as your lungs and internal organs get a small, but continuous bombardment of Beta particles which will eventually give you cancer.

If you are contaminated internally, with radioactive dust then there is no way to fix that.

Also nearly impossible to detect. No roadside detector will, anyway.

Well yes but only if destroyed. Then wouldn’t you call that a feature? When in their enclosures there should be no radiation.

No way could all the alerts be tracked.

Yeah, you bring up another angle to look at it from: even if the alerts didn't go off when the batteries are being used/stored properly, it would make it easy to create a lot of noise/false positives as part of an actual attack (were those batteries to be readily available).

They were for a long time, betavoltaics were used in pacemakers. They started using more conventional batteries because the betavoltaics far outlasted the actual pacemakers.

That's interesting. I imagine parts for an internal medical device would be able to be more tightly controlled than batteries for general usage, but maybe I'm wrong.