I've just returned from a gentle 8 mile Winter ride around some local backroads. Before setting off I've got into the habit of taking out my phone, starting up the Strava app and popping it back in my pocket.
As a result, my phone monitored the wireless signals from 6 geostationary satellites every 5 seconds duringf my ride and by measuring the time-lapse of these signals used some impossibly complex mathematics to compute my exact position on the Earth. Further calculations, that would have taken half a lifetime manually, computed the distance between each 5 second location and thereby derived a speed of travel. Each section of the journey was also compared to every Strava cyclist who had ever ridden it and placed me at the very bottom of a long database of names, and when I arrived back home an exact map of my journey was available on the PC with segments, comparisons and the state of the weather.
It is so easy to take all this technology for granted. I remember my school cycling days when the state-of-the-art technology was a "mileometer". This was a small counter as pictured above which was physically hit by a metal striker attached to one of the spokes - achieving any speed over 15mph involved a lot of "clanging" noise whilst resetting the thing to zero involved dismantling the counter and literally hours spent manually turning the small wheel until the zeros all clicked into place. The system wasn't very accurate at all and would not advise on the weather or tell you where you were on the map.
If my 15 year old self had been told "one day, you will carry a small device in your pocket which will contain the sum total of human knowledge and let you map your cycle rides into the bargain" I'd have dismissed them as science fiction fantasists.