We are still waiting technical info but as of right now the Official work on the SmartUSA web site is that the car can be flat towed behind a RV
Many of the RV aftermarket device places like Camping world sell the mechanical brake actuator that sits in the car and I expect that universal device would work.... I suspect it may be some time before there are any Smart fortwo specific devices. Rumor is Smart is working on a Smart approved front tow bar design.
I personally have dinghy towed a few small cars behind the RV but to tell the truth I prefer to put the small car up on a low cost single axle trailer.... There is no good way to back up with a flat towed small car
This car at 1600~1800 pounds will fit nicely on any of the low cost garden tractor trailers sold at Home-depot, Lowe's etc......
yes slightly more weight and this is not an option if already real close to max GCVWR ...
Here are the pluses of up on a trailer:
no mechanical additions or modifications to the Smart car
less tow resistance with the 2 trailer tires vs the 4 car tires
less car tire wear
less over all wear and damage to the Dinghy
easier to back up, into, or out of, tight spaces
The two real negatives:
Trailer cost.. while it is OK to use the lowest cost Lowe's 8x10 trailer; I would opt for the wider and longer one with electric brakes
An RV, and Small car, AND trailer get to be a pain to fuss with at camping sites with very little extra room.