I thought that was interesting too. Looks like the research on it came out 10 years ago. A couple of links from some quick searching. The second link has some charts and graphs, though it limits its estimates to 65+ age groups.

https://www.scientificamerican.com/article/walking-speed-sur...

https://jamanetwork.com/journals/jama/fullarticle/644554

Edit: I'd add that you likely don't need any tracker to get a rough estimate.

If you walk faster than people around you who are roughly the same age, then you'll likely outlive them.

That may be a reason to take it slow and smell the roses, since you have more time :)