The TuneLink is connected to a switched 12V outlet in the center console. When the car is powered on (running or ACC), the TuneLink is active and can provide power to the Nexus 7 via MicroUSB cable. I like the TuneLink because it features an auto-reconnect option that will re-establish a connection with previously paired devices that are in-range. The TuneLink also features an auto-resume option, which will resume playback of the current playlist/station/song/etc from your default media player (Spotify, in my case). As long as Spotify is running on my device, auto-resume works very well.
When I finish the installation of my Nexus 7 in my 2012 Pathfinder, I will try using Tasker to auto-start Bluetooth and Spotify upon detecting power, and then put the tablet in airplane mode when power is disconnected. Fortunately, the method I'm using to mount my tablet allows for very easy removal, which means I can take it inside and charge it there overnight if needed. Honestly, I LOVE this tablet! I originally planned on permanently installing it in place of the factory 7" touchscreen, but after watching this video , I decided on a different path. I'm about 70% complete right now, and will be posting my pictures and story here when done.