The only way to keep going in a power outage is to have a generator waiting behind the scenes ready to go when you lose all connectivity.
Except it’s possible to maintain complete connectivity in an outage, regardless of batteries or UPS.
Eventually the internet will drop, eventually you’ll have moment to power down all of your devices gracefully and eventually it will be just you and the pen.
What are you going to do when you can’t connect to anything?
What will consume?
What will you do?