Curt Echo Wireless Brake Control. If you have a truck you tow a travel travel with and it is not wired for the trailer brake control this really works great using an app on your cell phone to adjust the brakes to sync with the tow vehicle.
This one I have was probably only used 6 times at most. We bought a 5th wheel trailer, and I had to get a bigger truck that was wired for the trailer brakes. I see that they are selling new for $275 to near $300.