Ranger Pace Counter
Accurate. Works day or night. Functional without satellite, cell tower, or batteries. However, using the Ranger Pace Counter will require focus and baseline mathematical skills. So it's still not for everyone.
The strand of beads is a classic military and outdoorsman tool. Sure, we have much more sophisticated and precise distance measuring tools now, but the truly prepared will always learn the basics of land navigation because, as one reviewer points out, "GPS batteries do die." And a bracelet with plastic beads weighs a lot less than a smartphone or other handheld navigator.
The same Amazon reviewer, a 22-year member of the Green Berets named Matt, also provides detailed instructions on how to use the Ranger Pace Counter to gauge distance, as well as how to determine your personal pace count before setting out with the beads.