I originally thought I might be able to find a double suction cup to stick the glass of my iPhone 4 to the display in my Yaris. When I couldn't find anything right, I imagined mounting one of those spacer adapters run underneath the display to cover it.
Once I got them, I realized that I could shove one right into my CD player, and could easily install it and remove it with no damage. It's pretty sturdy, though the first couple of drives over big bumps, the phone would go flying, which is no good. Also, the charging cable doesn't fit quite right into the adapter hole, since those things are made for docks, not standalone cables. So I opened the hole a bit more and attached the cable to it, so it'd be a nice sturdy piece that can be installed and removed in seconds, and keep the phone from flying out.
You will need:
• Dock adapter
• Exacto knife & fresh blade
• USB car charging cable
• a car (preferably with a CD player)
Step 1: The Dock Adapter
Next, if you want to make your car USB charger fit more snuggly in this adapter, you'll need to trim the opening a bit.
I just took a fresh Exacto knife and carved out the inside of the hole. It's pretty soft plastic, and you can just carve away at it, while checking to see when the charging cable actually fits inside. Took me a total of 5 minutes.
Step 2: Holding the Cable in Place
Once you get it, wash your hands, take it out of the package, and massage it for a couple of minutes. Then, take about 1/4 or 1/3 of the small package and roll it into a snake. Insert the charging cable end into the adapter, put your phone on the other side. Then wrap the snake around the cable side, right up against the adapter.
You'll want to use your fingers to make sure it's all sticking together nice and tight. Don't forget to use the dull side of the Exacto you used earlier to push down the Sugru that's around the push-buttons on the sides of the cable, otherwise you won't be able to release your phone!
After you feel comfortable with it, carefully remove your phone. Leave your mount to dry for the next 24 hours.
Step 3: Putting It in Your Car
You may also be able to build on this and use the extra Sugru to mount it more permanently in your car.
I'm also considering getting some of those tiny stick-on cord organizers to run the cable nicely down the interior of my console.
Also, if the bumping around still happens, I may use a piece of scotch tape just to keep the adapter from bouncing too far up or down.
Good luck, and let me know if you build upon this project at all!