I have a samsung tablet installed on my car and this is how I did it:
On the tablet I use an app to create a rule and two profiles, driving and sleep:
Rule: When the car turns on it starts to charging the tablet which activate the driving profile
When the car shutts off stops the charge on the tablet which activate the sleep profile
Driving Profile - Turn on: wifi, bluetooth, 4G, change media volume and change screen brithness
Sleeping Profile - Turns everyting off and activate airplane mode.
Using this app my battery is always above 90%.
Now for the apps:
I don't use Google maps because it uses a lot data: I pay for the Garmin app, it was around $15.00
So tablet talk is an app that works over local wifi or bluetooth. It allows you to sync your phone to you tablet to make phone calls and receive texts on your tablet. Texting is a pretty straight forward process. Once enabled on both devices you press the menu key and choose the option to sync between devices. This copies all existing texts from the phone to the tablet. You can both create and receive new texts on the tablet.
So basically I use my tablet for everything else besides calls, which it can be transfer with th eapp above.
my 2 cents