There was a gallery of prototypes, and among them were some Zip-wire type vehicles. I used to play with cars and motorcycles as a kid that used the little plastic zip cord thing to rev up an engine. They pinched your fingers all the time, and the motorcycles went ape**** when you let them loose.
Clicky to check it out.
Not everyone's cup of tea but the kiddies will probably like them smashing around on the kitchen floor or flying off the table.