The general advice is that you should wash your hands for at least 20 seconds, or hum the “happy birthday” song as you wash. If you’d rather not look like a crazy person in a public restroom singing happy birthday to yourself, Apple has a solution if you own the Apple Watch.
With watchOS 7, Apple has introduced an automatic hand-washing detection feature to the Apple Watch. Based on the movements of your hands and other sensors and the microphone, the Apple Watch should be able to detect when you have begun to wash your hands. It will then initiate a 20 second countdown timer to let them know when to stop. If it detects you stopped too early, it will prompt you to keep washing.
While it sounds like a novel feature, this coronavirus pandemic has emphasized the importance of good hygiene and this hand-washing feature could still be very much relevant in the future, even when a vaccine for the virus has been found (and administered).