Ask HN: Describe the Perfect Smartwatch

I'm creating a new smartwatch.

I will probably start with off-the-shelf hardware (PineTime?) and focus mainly on the OS/UI/UX. I plan to make everything open source.

I'm looking for the opinion of experienced smartwatch users to better understand what a smartwatch should do.

What's your favorite smartwatch?

What do you like and dislike about existing smartwatches?

What are the most useful and important features?

What are unnecessary features and/or battery hogs?

Describe the perfect smartwatch.