One of this blog readers recently acquired a Radon detector as I had mentioned earlier. Specifically, the Airthings Wave. And wow, I am glad he did. As you can see from his screenshot, he first put it in one area in his basement (Waterloo, Ontario, Canada), and then relocated it to nearer the sump-hole. And there is a peak of ~1300Bq/m^3 (recall that the 'safe' limit is under 200).
Radon is a tricky beast. It moves in ground water (and we had a bit of a thaw yesterday). It comes in through cracks and holes. To check for it, you need to find the worst spot (usually the least ventilated area, and usually near your sump if you have one. Perhaps a cold room as well). And, it takes a bit of time to measure, you can't just snap it in an hour, it takes days or weeks to get accurate.
Health Canada has a nice FAQ on Radon, and a larger site with more information. 3000 people per year in Canada die from this, but many many more get lung cancer or other affects from it. Don't be one of them!
It seems BestBuy has removed the product (boo), but you can still get it from Amazon here.
Feel free to add in the comments if you have a Radon measuring system in place, and what your avg/peak is. And please remember, move it around a bit to find the worst area (least circulation/most moisture usually). E.g. don't place it beside the air-exchanger on your furnace and feel secure 🙂