| HHHmmmmm........
I have mixed feelings about the heart rate thing. It is good to keep track of. There are a couple of things I can think of about it.
1. It is a good measure of over-training.
2. Once you have an elevated heart rate in the morning it may be too late. Maybe the heart rate is a "time to take a week off" measurement. Not so much a daily training measurement.
3. I have noticed that when my daily testing method is dialed in, my heart rate in the morning never has enough variance to base anything off of. (a couple beats does not seem valid enough to base different workouts on)
Personally I believe that the test should reflect the preparedness of the nervous system.
I agree that the temperature method seems unreliable. So it really could not be used.
The Bulgarians, back in the 90's when they had the best weightlifting team in the world, would take a daily max in the Olympic lifts. That max would dictate what the training weight for the day was. The belief was that the body would wave intensity and volume all by itself. (of course I believe this only works well for more highly trained athletes. Specifically athletes who only train for their sport, not people with jobs and other things going on in life)
The Russians came up with measuring hand strength. It was found that hand strength was a fairly accurate measure of overall body preparedness. You would need a hand dynamometer to test for this.
What do you think about auto-regulating the specific exercises in a workout? How eould you go about doing this?  | 
