I THINK I want to buy one of these heart rate gadgets. Can you guys tell me what features you REALLY use? I know my heart rate will rise when I pedal faster, harder, or up hill...how will seeing this graphically help? I figure some sort of audible alarm to help me figure out which gear causes the least heart rate increase might be informative...still, can't you tell that when you can't breathe? --you just shift to an easier gear when your body says "no more of this!" :-) All joking aside, the only major benefit I can see from reading about these things is to actually keep me from over-training. Is this true? Finally, is there one watch that is useful in running, swimming, and biking...or do you have to get several different ones?