hi all. im new with smartwatch.

10 years ago i had a german made Heart Rate Monitor that can beep once whenever i reached 70% max HR and beep twice when i reached 90% maxHR. i dont know if current smart watch have this function. anyone knows?

i use it for intense mountainbiking so i need to be able to estimate my heart rate without looking at my wrist.

and also how accurate are the current smartwatch? should i trust them to read my heart beat when all they do is read wrist pulse?

thank you.