Keep in mind that USB OTG is a broken standard. Not everyone implements the interface the same and as a result you need a specific combination of device and OTG charge capable hub. I have messed with this a great deal. Even if the device shows its charging, the USB charge handshake may only be allowing minimal charge current, so your device slowly discharges while on. With the Brainiac product, I suspect that it is at least breaking even, but I think you also need to do some work to allow the device to power up and sleep based on the car power state so that you don't drain the tablet sitting in the garage and you have to use the tablet they are using.
The
Android car stereo that I installed is ~$45 more than that DAC alone and you still need to buy the android tablet device and the interface box. That's going to be way more than expensive and you still dont have basic car stereo features. This may be acceptable for you, but was a deal breaker for me. Most importantly - its not compatible with Navi models, which is the whole point of my project. Remove the Navi model limitations. Then any system is possible, including the Brainiac.