I am not without my phone when I am on the tractor as I have business to take care of via email and phone. I like having the phone mounted to the tractor and did with my Droid X. However I swapped phones and I am not going to spend $$$ on another car mount that is proprietary.
I did some searching for a universal mount and the only thing that I liked that I felt would grip the phone with all the bouncing was from a company called RamMount. They use a standard 1" ball and you can configure using several mount options from handlebar clamp to suction cup to screw mount.
They also have all kinds of stuff that attach to the ball like a cupholders, cameras, etc.
I thought it was cool.
RAM X-Grip™ Phone Mounts