Although this tutorial is based around the Asus Transformer tablet, it can be applied to any tablet and smart phone with ease. Also this was installed in a 1996 Dodge Ram pickup so the way I decided to mount the dock might not apply to your vehicle, but I'm sure you can come up with a clever way to adapt it to your car.
Items you'll need:
A wire coat hanger
Some aluminum sheet metal
JB Weld (And mixing dish and mixing stick)
Two bolts, nuts, lockwasher\
Two self tapping screws
90 degree angle bracket
Philips head screwdriver
Heat gun / lighter
Heat shrink tubing large enough for the coat hanger wire
Step 1: Cut Aluminum to Size
Step 2: Create Bottom Bracket
Next make another 90 degree bend about 2 - 2.5 inches from the first bend. Be sure to make this bend so that the first bend can lay flat against the back of the tablet as shown. This will begin the bottom portion of the lower tablet support.
Next make another 90 degree bend that will wrap back around the front of the tablet. I found that using a sharpie to mark where the bend should be made it much easier. For Transformer owners note that I am using the outer portion of the "dock slots" as a reference for how wide the lower bracket will be.
Next make another 90 degree bend across the front of the tablet, be sure that this bend doesn't cause the wire to come in contact with the touchable area of the screen. Then mirror the bends from the first end of the wire for the other end (Pictures clarify much better)
Once finished you have just created the lower bracket for the tablet dock.
Step 3: Create Side Bracket(s)
Now you need to cut out the portion of the hanger that would come in contact with the shoulders of the garment it would hold. This portion only has two bends in it. Cut off and discard the spiral portion that connects to the hook, then straighten the remaining wire as best as you can.
Again following the same general steps as the lower bracket, make the bends for the side bracket, again allowing 2 - 2.5 inches of the bracket to wrap around the back of the tablet. The final picture shows the second to last step, the final step is to cut the rear mounting points so that they line up end to end and don't over lap as depicted.
Step 4: Protecting the Tablet From Raw Wire
Since i was using small sections of tubing i was able to slide it onto the newly created brackets and finagle the tubing around the bends in the wire. Use your heat gun / lighter to shrink the tubing around the wire.
One subtle benefit that i noticed from using small portions of tubing is that you can overlap them and create better grip points for the tablet.
Step 5: Cut Back Plate, Mount Brackets and Drill Mounting Holes
First cut the back plate out of the aluminum. Use your tablet as a reference for how large to make it, i cut mine so that the tablet was roughly an inch larger on all sides.
Attaching the brackets is kind of tricky, I suggest doing them one at a time and letting the JB weld set before mounting the other brackets. Place the aluminum plate on the back of the tablet and then slide the bottom bracket onto the tablet so the back mounts are on top of the aluminum plate. Make sure everything is square and then apply a liberal amount of JB Weld to the two bend points as shown. Let the JB Weld set and repeat the same process for the side bracket(s) Note: I used my tablet to help keep the bracket at the correct position while the JB Weld was setting, this was the easiest way to make sure that the bracket would stay positioned where i wanted it.
Once the JB weld on the lower bracket has set you can then attach the side bracket using the same process as the bottom bracket. Again use the tablet to help keep the bracket in place while the JB weld sets.
After the brackets are attached go ahead and drill some mounting holes using your angle bracket as a reference for the spacing of the holes. You'll notice in the picture that the holes i drilled are off center, I did this because i didnt know if i would have to attach another angle bracket for additional support.
Step 6: Install Your New Contraption
Using the self tapping screws i attached the angle bracket to the lower portion of the dash, below the stereo and just above the 4 wheel drive shift knob.
Finally attach the mount to the angle bracket using two bolts and lock washers to keep the nuts from coming loose.
Finally slide your tablet in, plug in the auxiliary audio cable and enjoy!
You'll notice that i bent the corners of the aluminum in order to make the mount for visually appealing. The absolute final step would be to cover the aluminum with a material of your choice. I will be using the cloth from a reusable grocery bag in order to provide a clean look and protect the back of the tablet from scrapes.