At the risk of facing Croppi's wrath,
Yes thermal cameras are useful for finding leaks in UFH basically they guide you based on the temperature difference in the slab, also handy for showing cold spots in radiators etc.
While they have come down in price it is important you know how to use them, there are courses in thermography where last time I looked you can qualify at level 1, 2, or 3.
The reason I didn't buy one was the courses are / were fairly in-depth, a lot of studying required, equipment expensive and it was cheaper to hire in Gent who is fairly local to me.