As Westcliffe01 pointed out, vortex generators are pretty common in the aircraft industry. You see them on the top edges of the main wings, just aft of the point where the wing's curve really starts to flatten out.
Look carefully at the water's edge in a glass. It's not flat; the water kind of creeps up the walls of the glass at the edges. That's surface tension.
Air, like water, creates surface tension and clings to surfaces when its molecules are collected and moving (or staying put) together. This is a great thing when it's cold outside, because you get a thin layer of air that warms and clings to your skin. On an aircraft wing, however, it's like having a layer of molasses sticking to the wings and creating unneeded drag. The vortex generators perterb the air, get the molecules to run in opposing spirals down the wing's surface to break the surface tension, increasing both the amount of lift the wing generates and increasing the speed and fuel efficiency of the craft.
Will it work on an RV or trailer. Absolutely . . . but.
RVs aren't like wings. They already have lots of little things sticking out, like vent covers, window trim, roof vents, air conditioners, solar
panels. All these things hit the air as the trailer moves through it, kicking it up into a turbulent, non-cohesive mess. I guess it's conceivable that the turbulence might subside somewhat by the time it gets to the back of the RV, but the abrupt, non-tapered end of the RV would tend to do that anyway. I doubt this product does much in terms of drag reduction or improving gas mileage..