I can't help but think that for $10 I could buy a hydraulic jack from Harbor Freight, and mount a pressure gauge on the side....pressure times the area of the jack's rod equals the force exerted.
Or I could take my regular 200 pound household scale, put it under one end of a 4x4 beam, put a pivot under the other end of the 4x4, and drop the trailer tongue on the 4x4...make a couple of measurements and voila. Just saved $100 and didn't have to switch to Geico.