Modern vehicles have lots of onboard systems each with their own controllers, not all of these go to sleep when you lock the vehicle. Alarm, immobiliser, wireless entry, remote control and status updates to yourphone etc. all consume power in the background. I have a battery float charger now, and connect it up if the vehicle is not driven enough.
However, since the vehicle (at least on Excel spec) reports status back to a smart phone app, wouldn't it be a good idea to warn the driver when the battery is in need of charging BEFORE it goes flat?

Interestingly, my battery problems started a week or two after an "Over The Air software update". I received a letter saying Toyota would remotely update software in the vehicle and not to panic if refused to start while updating.
So will we be experiencing the same as PC users getting updates? A progress bar graph and "Please wait while we update your vehicle"