Hi Al B,
your robot looks really cool. Two-wheeled robots are really popular these days.
I've been using the same phone holder since you gave me the link. But for my new outdoor robot, I will be using a solid but slightly more expensive mount:
I finally had the time to build a rover based robot using the 4wd Dagu rover 5, its motor driver board, the IOIO OTG, and the same pan & tilt unit I used before.
It's a nice little platform for indoor but it's a bit slow compared to my old RC car ;-)
But I'm going to start building a 6WD wild thumper ABR next week for an outdoor search and rescue project so that should be fun. I'll take some pictures and videos once I'm done.
Best,
Nicolas