My pixel watch 2 has a weightlifting exercise timer... But it doesn't really tell you much, it just helps you adjust your calories for the day.
The most helpful thing is the heart rate monitor and skin temperature. These things tell you when you are exerting yourself the most. Today was chest day for me and I got to 148, shortly after doing 90kg for 6 reps. This value is actually kinda low for me... I've seen it hit 175 when doing heavy deadlifts. That said I wasn't trying to go too heavy today, I wanted more reps. I did 60kg for 15 reps, but that is muscle fatigue and less heart rate...
Hope this helps.
