How close are we to a wearable that can track calorie intake?

Relevant article on the difficulties of calories tracking. https://www.economist.com/1843/2019/02/28/death-of-the-calor...

Tracking calories is a pretty annoying task but the good thing is you only have to do it for like a week, then you have a good understanding of what your calorie intake is.

I can't see a practical, easy to use and accurate solution to that (using 2020 technology at least)