So your key fob battery dies while you are doing 80 on the Washington beltway ...
Won't affect anything. Your drive will continue as normal. You won't notice that battery is dead until you go to start your car up next time.
As a preventive measure, I have the battery replaced in my key fob every couple of years while I'm getting the car serviced. I believe they will last 3-4 years as a general rule.
The rfid chip doesn’t need batteries to work.
Good point. Perhaps give a verbal and display warning with a “Push button to keep going” option?