Here's a 10x better way to do the same basic idea: get a bag of candy for yourself. and every 5 minutes they are well behaved, give them a piece.
I hate that the reward here is candy because I absolutely detest sugar. And in this scenario I'm conditioning my kids to eat candy when they do good.
I try to reward good behavior more so than I punish bad behavior. Things we're definitely simpler when they were younger but now they lie and make up stuff. I never lie or make stuff up. So, where does this behavior come from? And I never punish them for telling the truth.
But the idea that the bag is some reward and that you can lose some of it if you miss-behave and then maybe earn it back. That's reasonable.
I typically employ a progressive punishment in the form of a timeout. Go to your room for 5 minutes. If they don't respect that, it's 10 minutes up to 15 minutes. Culminating in: no iPad for you today.
Sometimes I ask them what the consequences for breaking the rules should be. And I get very reasonable suggestions.