On my 12SRT you could pull the key out of the fob(just like the Hellcat) to gain access to the car if the fob stops working. On the 12 you could pop out the push button start and stick the end of the key fob in to the hole and turn it just like a key to start the car.
The question is, what happens with he Hellcat if the key fob stops working? Are we stranded?
Also on the 12 you could pop a little panel off by the shifter and stick the end of the fob in to shift it in to neutral in case the battery was dead or any other reason the car would not run