I think there's definitely a market for endurance athletes. Runners and cyclists would like to see time, speed, distance, cadence, power output, navigation, etc without having to look down at a wristwatch or bike computer. Those people are accustomed to spending a lot on sports equipment. There are existing products like the Everysight Raptor and Garmin Varia View but they're bulky or goofy looking or obstruct vision…
I agree in general that it would be useful in these situations. As someone who wears glasses, I find it impossible to run with them because of the movement or them just falling off. Are people who wear glasses able to run with them - am I doing something wrong?
Get a strap for your glasses and have it pulled fairly tight to your head. They are cheap. One similar to this. It needs to be the correct shape for your glasses frame so it's probably best to go to a real store and try a few straps in person.
https://www.amazon.com/Peeper-Keepers-Eyeglass-Retainer-Hold...