When you roll a 1, an effect triggers. If you don't roll a 1, the next time you roll for the effect it triggers on a 1 or 2, then a 1-3, and so on. When the effect triggers, reset the count back to 1. I've used this for 'wild magic' effects where you roll each time you cast a spell, but I think it'd work for lots of other things! The one that immediately comes to mind is your spaceship's engines overheating if you keep pushing them.