I used one for years. I bolted it to the frame of the tt and looped the cable thru the bikes and genny. worked great for a couple of years. Rain must of caused the spring inside the unit to rust then break. So the cable wouldn't retract. I removed the device and returned to an old fashioned cable and lock.
I don't know if the new ones are better. If they improve it, I'd buy another. But from what I've seen of this one, its the same.
2000 Cherokee 29BH with 6V batteries, LED lights & 400 watts of solar power, flipped axles and raised. 2007 Tundra 5.7L DC-LB with lots of mods. C-co, 8/158th AVN Maint.