I find my VHR does a remarkably good job of nailing resting heart rate (rhr) day in, day out.
My resting rate is in the 44-48 range, and usually happens within two hours of waking. I have been fascinated about the jumps during the day.
Sometimes getting up for coffee will result in a jump to over 100. An overnight awakening will show a rate jump to 70 or so.
It's not a smooth graph. This is from Tuesday. The exercise and sleep periods are pretty clearly marked on the top of the graph. To the left of the first alarm clock is a sleep period; to the right till the "zzs" is a waking period.
You may be interested in DC Rainmaker's post on rhr.