https://wccftech.com/apple-watchs-handwashing-detection-feature-in-watchos-7-was-in-the-works-for-years/

Apple introduced a very interesting feature with watchOS 7 that can detect when you're washing your hands. However, the feature is not something that just came out of the blue and Apple decided to make it part of the release. As per Apple's VP of Technology Kevin Lynch, the company has launched the handwashing feature in watchOS 7 after "years of work".

Samsung is one of the fastest early adopters of the feature as it added a handwashing app to its smartwatches. However, we can be sure that Apple's implementation is far superior to the competition at this point in time. The handwashing detection feature will be automatically initiated when a user starts washing his hand. The Apple Watch will display a 20-second timer on the screen that users can make use of to wash properly.