They copied one available by company called Seek. I got one last yr. works pretty good. Didn't use in tracking since my buck died not far in daylight. Any thermals work best with cold temps so you have differentiation.
My buddy has a high dollar Flir hand held and my Seek worked as well considering it's size. Pretty cool to play with in the dark. Seek also makes a handheld that came out after mine. I bought mine EBay for 200$.
I've been with my buddy using his to find deer at night. Worked great. Again best if cold weather and even if trees are warm from sun it can be tricky to read. Here's pick of mine and dog in complete dark.
I don't think it would work well on a blood trail. The blood spots would be cooled and look like the surroundings by the time you would be on the trail. The carcass would be different and you should be able to see it fairly easily on a high temperature differential night. A hot day would still be difficult.
Some soil health folks use the infrared iphone cam to monitor soil surface temps.....thinly vegetated hot areas will be red/orange/yellow and thickly vegetated cool areas purple/blue....it is a way to train your eye for proper vegetative cover.....but the down side that I saw is the color of above ground material also absorbs/reflects light/heat so it is not a true depiction of soil temperature. They also have microscope level magnifying lenses so you can see fungi and macro fauna in soil (100x needed) or chiggers on your skin. https://www.google.com/?gws_rd=ssl#q=microscope+lens+for+iphone