I bought and sold one of the Leupold LTO thermal trackers. I thought I would possibly be able to use it to help track a wounded animal at some point but it wasn't very effective. I could barely even make it useable looking for my dog in the yard at night let alone trying to scan a hill and seeing animals in cover during the heat of the day. Most outdoor terrain is variable and has lots of different things that retain heat at different rates (rocks, trees, leaves, dirt, etc.) and it was very difficult to actually see anything for me. I could place my hand on a flat table and look at the table after removing my hand and see the heat signature of my hand and that was cool but not very practical. I think some of the super high end stuff may be better, but for the stuff in the under $1,000 category I wouldn't expect to do much but play around with it.
As a side note - what about optics in general? Isn't it a huge advantage to have someone using the new Swarovski BTX and 95mm objective off a tripod scanning a hill to see where the animals are? Compare that with someone scanning with some cheap Bushnells or Nikon Buckmasters or something like that.
When these topics come up I always wonder how spending $6,000+ on high end optics is perfectly fine for fair chase for pretty much everyone but mention a drone or thermal imaging or a trail camera and the whole thing blows up.
As someone who has had a pretty decent drone ($1k+) and a low end thermal device (fairly equivalent to a FLIR), the high end optics are going to give a much bigger advantage to someone than if you were using a drone and thermal device in the current form. There is a chance that drones and thermal devices will improve and provide a bigger assistance in the future, but right now if you gave me a choice between a drone, a FLIR or top of the line optics to use for hunting, I would take the top of the line optics.
My 2 cents. Nathan