Flexwat is heat tape. it is pretty much the same thing as any other UTH, but it is a much simpler packaging. Yes it needs to be on a thermostat. Flexwatt can get unto 120 degrees.
This is what it looks like:
The black lines are the resistive heating elements. They are very similar to the windshield defroster on a car. Electricity passes through the black part and it turns the electricity into heat. I highly recommend it because it is much cheaper and works better.