Here's a link to the mid-engine model's page on the company's web site:
http://travelsupreme.com/motorized.php?page=main&id=94
On the top right side, click on the first photo in the photo gallery to see a picture of the Smart car in its trailer garage. The page says it has a motorized lift to load and unload the car, and that the space could optionally be configured as a second bathroom instead.
My guess is that this would probably be the most expensive accessory you would buy for your Smart.