What happens if someone else gets hold of your AW9 or any w Wallet ability?

So I have the AW9 which I bought almost two years ago. I have all my credit cards added to my wallet in my iPhone so they’re also set up on my AW9.

All I have to do is just double click my crown and I pay for items on my AW9. What is to stop someone else who has my watch from doing the same and go to town in buying everything in sight?