Simply by sharing a nickname with them.They will be able to follow you in real time on the map and monitor all your data:

Position
Average speed
Current speed
Kilometers traveled
Time spent
Weather information
height above sea level/km
height above sea level /time
Ascent / descent / plain

They will also be able to see pictures of your current location with StreetView.
The app does not require registration, the nickname chosen at the time of use guarantees your privacy and you can change it when you want.
If you decide to use the app to track your rides without sharing them, it is possible to do simply putting the same nick in "your nickname" and "followed nickname"(settings options).
App needs for permission to track location in the background.