Hi @LX1FU.
It's not possible to have voice cues but you can have the watch vibrate after each lap (you can set what you want a lap to be, in your case 1km).
Selet the exercise app on the watch - tap the exercise that you want to use - swipe up from the bottom to access the exercise settings - scroll down to laps and select "Auto count" - select lap rule "Kilometres" - select 1km - now swipe back upto the top so that you can start the workout. You should now receive a notification after ever 1km.
Best Answer