I built my own from gas pipe and elbows and some velcro. It works great in my work truck but if you are going to use it off road then you would need to use something stronger than velcro.
I work for a company in Chapel Hill and thats what we do is install computers and all in cop cars and all, jottodesks won't hold up to much abuse. We use all Gamber-Johnson mounts but they are very high dollar, but like everything else you get what you pay for .. thats my opinion anyways
I use RAM Mounts in my TJ for GPS, Scanner, etc. There is nothing like them. They are a little pricey, but nothing has fallen out of its place yet on the trails...my vote would be go RAM...