This thing can never be "accurate". Proper instantaneous measurements for radiation require more than a good detector. The operator is part of the equation.<p>Say you have two pieces of fish in front of you. Answering the question "which one is more radioactive" requires more than holding a device over each for a couple minutes. You have to think of the flux, the surface area of the fish visible to the detector, the orientation of the detector, any background sources, the mass of each piece and most importantly the distance between the fish and the detector. That cannot be built into a hand-held consumer product. Absent that, these devices will only scare people.<p>Note the pic in the OP showing the detector plugged in via an extension cable. I'd bet that they moved it around until magically it's measurement lined up with the other device.<p>Also, low levels of radiation are nothing to be concerned with. The linear no-threshold model (the direct relationship between radiation and cancer) is no longer considered appropriate when discussing very low levels.
Checking food with a gamma radiation detector is not too useful. [1][2] Some "preppers" are into this, and get excited if they count for an hour and get 20% higher than usual. They're probably seeing ordinary variation in background radiation, which varies over the course of a day.<p>A tester called LANFOS has been developed in Japan, to deal with possibly-contaminated food from Fukishima. It's a round pot-like device with shielding and plastic scintillation detectors into which a sample can be inserted. This has been tested against other methods and the results agree with standard laboratory tests.[3] That's a practical solution in an area where you really do have to test.<p>If you're worried about suddenly encountering a big gamma emitter or X-ray beam, get one of these.[4]<p>[1] <a href="http://www.bloomberg.com/news/articles/2011-04-12/geiger-counters-to-find-radiation-in-meals-may-be-meaningless-" rel="nofollow">http://www.bloomberg.com/news/articles/2011-04-12/geiger-cou...</a>
[2] <a href="https://www.princeton.edu/~ota/disk3/1979/7907/790720.PDF" rel="nofollow">https://www.princeton.edu/~ota/disk3/1979/7907/790720.PDF</a>
[3] <a href="http://www.foodqualitynews.com/R-D/Radioactive-compounds-detected-through-LANFOS" rel="nofollow">http://www.foodqualitynews.com/R-D/Radioactive-compounds-det...</a>
[4] <a href="https://www.amazon.com/NukAlertTM-radiation-detector-keychain-attachable/dp/B004SZ2HXQ" rel="nofollow">https://www.amazon.com/NukAlertTM-radiation-detector-keychai...</a>
I'm actually reverse engineering this and similar cheap sensors as part of creating an iOS app... I'm significantly motivated by how utterly <i>pathetic</i> their companion apps are.