You can use Flir to see infrared, but it's only really a novelty. If you have an older Camcorder kicking around, you can use its built-in Infrared instead.
An infrared camera is useful to diagnose TV remote controls too, but you don't need Flir to do this: Your iPhone already has an Infrared camera - Androids too! Check this out:
I put my TV Hardware (PVR, etc) in the closet out of the way so that I could have a super-clean installation of my TV on the wall, with no other visible hardware, cables etc.
The problem though is that the remote control uses Infrared (IR) to communicate with the boxes and therefore require line-of-site. With the boxes in the closet, I can't change channels, etc.
So I bought an IR extender that extends the IR signal over HDMI. I hooked it up and saw that it didn't work. So what was the problem? How could I test the IR extender?
Surprise! I was able to use my iPhone to do it. Here's how. (This should work with any smartphone camera too).
The main camera on the back of the iPhone has an IR filter on it to improve the picture quality, but the front-facing camera does not. So if you take your IR remote control and point it at your iPhone with the front-facing camera on, you will be able to see the IR LED flashing on your iPhone screen!
So to test my IR extender, I disconnected it from the TV and Box, and connected it to opposite ends of a spare HDMI cable and sure enough, no flashing light from the IR extender emitter. The product is a dud.
When I returned it to the store the guy gave me a bit of a hard time until I proved it to him. He gave me a new kit and it solved the problem.