Pilot FriXion pens use ink that turns clear when heated to 60C (140F), so you can use any soft plastic or rubber as an eraser, by raising the temperature with friction. I use a Frixion pen as my everyday workhorse, so I’m always careful to never leave my planner in a hot car.
However the Law of Attraction planner turns that drawback into a feature (skip to 1:27).
I have mixed feelings about this. I’m not one to go back and read old planners, but erasing the past seems kind of . . . blasphemous? I know you can save it in the cloud first, but dude, you’re nuking your planner i.e. the actions of a human about to kill their spouse and grab a flight to Belize with a Samsonite suitcase full of non-sequential cash.
Also, better not live in Alaska. Or Maine on a bad day. At -10C (14F) all the ink comes back.