I own multiple smart watches and standalone GPS devices and yet I don't bring them with me when I'm doing long distance hikes. This is because they are a hassle to keep charged and I always seem to forget to start the track when I leave camp leaving my stats for the day off by however many miles.

 

My general advice to new folks is just get a new ish modern smart phone and use that. If FarOut exists for the trail it's everything you need to hike. If it doesn't exist I generally find a gpx for the trail and load it into Caltopo or GaiaGPS. Both applications allow you to generate waypoints every x miles along a track which I then use to make mile markers. I then use these mile markers in conjunction with a Google Spreadsheet.

 

Previously I made this spreadsheet by hand every year and it was bloody annoying. Being the lazy ex software engineer I am I've now created a template complete with a script to generate all the manual bits. Easy eh! See below the cut for how to use it yourself.