I don't think there has ever been a product sold without an extensive legal mumbo-jumbo making sure you have no chance of wining a legal battle.
When this thing is used in critical/life stuff the company that makes this product probably does it's own testing.
Or they get written approval as part of the contract. These aren't exactly the type of devices you buy from Digikey.
I think it is interesting to find out that there is such a thing. How do they do production testing? How would you know if it works or not?
I believe it just detects radiation, so they could use a calibrated radiation source, the same type as used for Geiger counters.