I know, it's no fun, but... An ANSWER to Eric's question! (and mine,
too)

KSport makes a hand brake for rally cars which is a hydraulic
actuator. It has a lock, so can be used as a parking brake.
Believe it's T 'd into the hydraulic lines between the actuator and
the axle
http://www.ksportusa.com/asp/hydraulic.asp
Ever try moving a trailer around by hand on even a slight slope with
no parking brake? You can't run to the axle to chock the wheels in
time.
Better bring chalk!
Jim