A heart rate monitor is a great thing to have even if you aren't doing research about efficiency. It appeals right out of the box, when it asks you to customize it for yourself- After that, you feel as though it knows who you are. You input your:
Weight - 166 lbs
Height - 6' 3"
Birthday - July 23 1982 (I wonder what it will get me)
Sex - male
Activity level - Top (5 days per week)
Sign - Leo
Max HR - 197
Resting HR - 50
V02 Max - 74 (As predicted by Polar's OwnIndex technology)
The cool thing is, it can turn any activity into an effective workout. You say how much you want to exercise, and it calculates a workout routine for you, with, say 4 days a week of exercise. It would then prescribe one short, strenuous workout, two normal workouts, and one long, relaxed workout (and you just keep your heartrate in the correct zone for the right amount of time). Its so cool to ride with, since you can watch your heartrate in real time--rising as you pour on the effort or ride up a hill, and falling when you coast or ease up. It might sound obvious, but its a joy to know what your heart is doing when you ride (especially after being used to tachometers on motorcycles).
I learned that I had been training at much too high a heartrate on "resting" days. This thing is a great training tool.
At the beginning of each day, I reset the trip meter on the cyclocomputer, and put the heart rate monitor on. It measures the calories I burn during the ride. Whenever I stop to eat or ask directions, I pause the heart rate monitor.