Love my HR monitor. They are necessary to get an idea if you are exercising too hard or not hard enough. (When running, my HR was always too high--cycling too low. I have to do hill workouts on my bike to get it up). After a few weeks, you will be able to tell your exertion without it. I still use it to see if I can pick up speed with a lower heart rate. I have a Garmin Forerunner with GPS and heart rate monitor.
"Well-behaved women seldom make history." --Laurel Thatcher Ulrich
'09 Trek WSD 2.1 with a Brooks B-68 saddle
'11 Trek WSD Madone 5.2 with Brooks B-17