Researching and it seems they might be less useful due to difficulty in quickly finding tension data for the belt you want to tension. Anybody use one and are they useful and fairly quick to find tension specs and enter data?
There is no point with serpentine belts or anything with a spring tensioner.
I used to do maintenance in a large industrial plant and the didn't use them. They tried once but there was to much noise and vibration for it to work properly.