I just bought a Pelouze 110Lb scale from 3 rivers, it cost $45. I am happy with it, but have nothing to compare too.
I put a hook in my tree, attached the scale to the hook any my string, put an arrow shaft on the bow with a 28" mark and pull it to that mark. Then my wife stands on a small ladder behind (to get a level reading) and tells me what the reading is when i say when (28" draw)