I helped out our local MB dealer last weekend(and this coming weekend) and the owner of this company was there showing his product. It was a pretty cool setup. Looked like it was really well built and functioned good as well. The owner, Ted, really seemed like a good guy. Might be worth some of you checking it out. Basically you use a crank to roll the trailer front to back, the arm to steer and it has a brake so you don't really need chocks(unless a really steep grade I suppose). It also didn't seem all that expensive for what you get at under $400. Might save that in trailer and boat damage alone.
http://trailervalet.com/