I wanted to be able to use my laptop tethered while shooting. I looked into a couple of commercial laptop trays, but they were kind of overkill. I used an extra Bogen Magic Arm and some plywood to make a usable platform. I cut a piece of 1/2″ plywood slightly smaller than the footprint of the Vaio laptop and inserted a 1/4″-20 threaded insert into the center, dressed it with some black gaffer’s tape, and made a strap out of velcro. It gave me a stable, adjustable platform for the laptop.
Warning, don’t try clamping something like this to a carbon fiber tripod. This is a stout, aluminum Gitzo which can take the compression from the SuperClamp at the end of the Magic Arm.