Many aircraft have brake temperature indicators in the cockpit - if you can communicate with the crew via a plug in headset they may be able to give you brake temps. If you want to point an IR device at a brake unit do it from in front or rear of the wheel assembly - not from the side. as when a tire lets go that is where most of the fragments go. There will be no hotspot on an individual brake - the rotors and stators are just a large mass of hot steel or carbon.