Yes, it's junk. It's yet another random gadget for our car we don't really need, but for some reason, really want. It's called the Battery Brain and it's a little box that attaches to the positive terminal of our battery. It monitors the level of charge in the bigger box that helps us to start our car. If for some reason, like we left the lights on (again) and the battery reaches the lowest level required for the engine to start — our second brain kicks in and stops the battery from sending more charge until the car starts again. Not a bad idea, especially for those of us dumb enough to leave our indoor lights on for a weekend. Would that be us? Yes, yes it would be.
Battery Brain, For Your Ride [Gizmodo]
Subaru Parent's New Hybrid Battery Reported to Last 150,000 Miles [internal]