Can any Apple watch bands add extra features? I've got an Apple Watch series 3, and was wondering if any bands support extra "features", and don't just change the look?

For example, is it possible that any bands exist that enhance the vibration only mode so vibrations are stronger?
I have a vague recollection of several attempts at "feature" bands when the original Apple Watch was released but I'm not sure many of them even made it into production. The only one I'm familiar with that is a shipping product is the KardiaBand.

https://store.alivecor.com/products/kardiaband

It adds ECG features to Series 3 watches and predates similar features in the Series 4.