So the radio in my car was slowly morphing into a paperweight as if it was some sort of electronic Pokemon. It rarely worked properly and when it did it wasn't for long. I decided on removing the thing and replacing it with the Nexus 7. I mostly did this just to see if I could as well as to see how useful it was. Now, people have done this in the past many so this wasn't a road untraveled. After much reading and planning I came up with this diagram:
Mind you I have no electronics background (or blog composing background so excuse the terrible writing). The plan looked good, so the parts were ordered and surprisingly everything worked very well.
The Nexus 7 runs a version of CM11 with a custom kernel to allow the thing to both charge AND act as a USB host. It also allows the use of a USB DAC (fancy term for an external sound card). I tried plugging the 3.5mm audio cable directly from the Nexus to the amp but it sounded like garbage so went with the DAC. The equalizer isn't really needed but I went with it anyways.
On the diagram you may have noticed "Backup camera". YES! It has a backup camera, the only caveat is you have the press the little camera button on the screen for it to open. I'm trying to figure out a way to trigger the camera with the reverse lights but that's for another time. So for now I have a small webcam by the license plate (forgot to take pics but just use your imagination).
The External storage is just a thumb drive for now but I'm going to experiment with a portable 2.5in 1TD hard drive I have once I get a chance however it might be too much a drain powerwise.
A huge part of the operation is a program called Tasker. It's an insanely powerful tasking program for Android. Basically once it notices a power/charge (by turning the key) it turns on the following: Wi-Fi, Screen to 'Always on', Volume to max, GPS, and turns off Airplane mode. When I turn the key to the off and the charge stops, all of those things turn off to conserve battery and it goes into a sort of deep sleep mode. Very neat program.
Also, there are two cigarette lighters; one that I wired in with the stock lighter that sits behind the nexus and the other is the main one on the dash that charges my phone
I'm currently stationed in Japan (USAF) and the radio here is horrendous so I mostly just stream via Google Music, Tunein, ect...
The only real 'issue' is the Nexus 7's screen is polarized so when I wear my polarized sunglasses it sorta is impossible to see but beyond that it's the cat's pajamas. I'm sure I glazed over a lot of the details but that's the jist if it.