The only one I have seen on Ebay that I would trust is the one that mounts to a seat bolt in the car.
No cup holder, suction cup or especially vent mount for me.
If you are looking for a good branded solution, then check out RAM Mounts. They offer lots of good robust solutions for mounting mobile devices (including lots of tablets) inside a car.
This is the best, most solid mount I've ever seen.
Amazon.com: Panavise Custom InDash Mount for Jeep: Cell Phones & Accessories
We used one in our Miata, and I've ordered one for my Nissan Cube.
It mounts to the dash frame where the radio is screwed in, for some models you don't even need to do any drilling.
Panavise makes them to be custom fit for specific vehicles, and sells them for $33 plus shipping, but on Amazon other sellers want $18 to $20 plus 2 1/2 to 4 bucks to ship.
You'll need to get something else to hold your electronics TO this mount, but Wal-Mart or Pep Boys will have something for not much.
Panavise.com if Amazon doesn't list one for your car.
I bought a mount for mine on eBay... do a search... got a suction cup mount... I have used it in my car... If you do offroading,,, probably would not work bouncing around...