I've had a problem with skipped/extra heart beats, which I talked about in this thread:
http://www.bikeforums.net/showthread.php?t=125068

I dug my 10-year-old bottom of the line Polar HRM out of the closet to see if I could notice the irregular beats on a ride. But it only gives a reading every couple of seconds or so, which isn't enough to tell. Can any recommend a HRM that takes frequent enough readings to notice this, as well as be able to download to a computer in case I need to do a printout for the doc?