Wow, I am shocked by the amount of questions that I receive every time that I mention my heart rate monitor!
It has been one of my best purchases in my quest to get fit because it makes me work so much harder and tells me when I am coasting. I don't have a preference of one over another because I only have used the one.
The biggest thing that I was looking for though was one that kept a constant heart rate, not just one that I could use to check my heart rate. I have a strap that I attach around my chest below my sports bra so that I have a constant read going to the watch. I knew that I could hold the handles on the gym machines and get a read but that wasn't what I was looking for. They are a little pricey but I am SO glad that I splurged on mine. It is the Polar RS100 but I am not sure if I would have done more research if I would have gotten this one as it is designed for running. I later found out that they have ones geared more towards losing weight than mine was. I think that those ones are more pricey though. The polar site has a comparison questionnaire that may help you do more research.
I love polar though because it links to the machines at the gym so that I can just look at the machine screen rather than my watch to know where I am at.
The greatest thing about using one is that it is programed for your individual body.
I type in my resting heart rate, height and weight (just the first time). It gives me a much more accurate read on how many calories I have burned.
I like to keep track of my calories burn and think for every 50 calories I have burned a point! If you are trading out these points it isn't quite the same math though. The equation I have been told is
weight * how many minute you worked out * .000807
It may be less but really how many points do you need to swap anyway? I was also told that the max number is 4 per day.
Ladies I really hopes this helps answer any questions you have.