I have both a FLIR i7 thermal imager and a Milwaukee snake inspection camera.

I'm eager to see if they will be helpful in beekeeping, but that's not why I bought them.

The Flir costs $2k and is exquisitely sensitive. I have gotten a thermal image of a forager with it, and it clearly shows the thorax is at nearly human body temperature. Handprints and footprints show up easily. What I really want to try is to see if the camera can spot exactly where bees are when someone else (not me) needs to do a cutout. You frequently CAN spot studs in a wall with this type of camera.

I'll try the i7 on thermal plumes at some point. They will not generally spot variations in air temperature, but they will spot steam ... water vapor absorbs strongly in the band they use, and steam from boiling water or exhaust rising from a propane heater looks like flames on the display. If the plume is sufficiently warm and humid the i7 MIGHT just spot it. But heat from an opening such as a top entrance is a piece of cake. That's a perfect example of a cavity emission, right up the alley of a thermal imager.

This morning we went for a hive inspection with our mentor. He is concerned about the possibility of swarming, but it was windy and marginally cool this morning and he was reluctant to open the brood chambers. It had not occurred to me to bring the inspection camera, but it occurred to me on the way home that it might work to peek in the entrance to look for queen cells, particularly if you only have one brood box installed. My camera has too large a head to fit between frames, but I've tried it on an unused hive and if you pull the entrance reducer it has no problem going into the bottom of a Langstroth hive and checking the frame bottoms.

I would not buy one just for that, but it might, on occasion, be better than wallowing on the ground with a flashlight looking in the entrance for queen cells or general activity. That's a poor substitute for a proper inspection, but if conditions are poor it might be better than nothing.