Product review (4 stars): Needs a better mounting solution. Very good freezer monitor
Freezer Meter Frozen Food Safety in Seconds

My main problem with the design of the freezer monitor is the Velcro strap as the only mount option. My Samsung fridge has glass shelves and smooth walls. I cant find something to strap this too. I jury-rigged a mount but its not optimal. It does provide a great service in areas, like mine, that loses power on a too frequent basis. The place a quarter in a frozen cup of water is a more vulnerable DiY solution. This one is sealed and won't cause an accidental mess.

Id suggest a 3M tape hook to hang it from or a silicon stand to prop the tube up, vertically. I still like its function, low cost and leak proof construction.  Its also easy to see the marble dropping into the water if it melts. It is also very difficult to find this device if you don't search the actual name. If you can easily strap it to a shelf this is a cool, so to speak, device.