These have been around for a long time. I once considered buying one but had concerns about possible eventual damage to the jack leg if it was frequently forced to slide sideways while under full load. FWIW, I've never known anyone to own or use one. I would think that they would be very popular if they worked well.
Happy Camping! ///// Richard D.
2006 4x4 Ford 250 SD / 2007 Flagstaff 827 FLS
One very patient wife and one furry child who travels with us. Forty-two years of trailering and camping, and I still have a blast.