Like others, I have used a heart monitor as a training aid until I, too, got the feel of where the rate was. I have used the monitor on several hikes but really only utilized it to check my heart's recovery time from near maximum back down to a near normal rate. An example of where I would do this is would be after a steady (no stops) crank up South Hancock's steep trail and when I got to the top, see how long it took to decrease and level off. Other than that, it now occupies a spot in the top dresser drawer.
JohnL