i once used my mountainboard leas when my brake went missing (apparently the screw loosened op and i simply lost it somewhere on the hill... (or someone stole it while i was in the lodge....)
so if you have something like that from a kiteboard or surfboard you'd be settled... you can use a carabiner or boltsnapper for quick releasing when taking gondolas....
(ps: be carefull on rails and don't put a bombproof leash around your legg, make sure it 'll brake or come off if it needs to ! )
On a sidenote: i once went looking for a runaway snowboard only to find it all the way down the run embedded almost 3inch deep in an old tree and broken in half.... you can only imagine what it'd be when it'd hit a human....