I have a Garage dashboard that shows the state of the garage door, garage lights, and the presence/power state of each car. (Using this driver for the Tesla, and this Zigbee device for my wife's ICE.) Presence is the presence template, obviously; the Attribute template can be used to display the powerSource.
It's kind of ironic that my rules have to have inverted logic for each car -- the Tesla switches to battery when it's getting ready to leave, but when the ICE car stops being on battery, it's preparing to leave. 
