I used to wear a heart rate monitor. I hope to again this year (I need to get the batteries replaced). The only tough thing for me is I don't like to wear an HRM during Yoga. I also do not typically wear it during skiing, hiking, and snowshoeing, or even ice skating for that matter. A Polar HRM is the best brand out there that I've seen. I'm also a bit biased since I used to work with Polar.
If you are considering a Polar for 2012 you'll find that Amazon.com has the best prices. Polar also features a free website for logging your workouts and tracking your progress. Back when I got my first Polar you needed to buy a separate device for the logging. Since Polar uses a chest strap it is more accurate than any other type of HRM. Wrist only does not log an accurate burn. I know research tends to go one way or the other in terms of the 'fat burning zone'. For me, it was just a nice way to know what I was burning.
I also suggest this site for figuring out what you burned on a hike or out on the bike or pretty much anything. Last winter with all of that snow I logged what I burned shoveling. The snowbanks were over my head at one point so I wanted to log all of that effort.
Some of you may be wondering "why log anything?" or "Does it really matter?" It turns out, it really does matter if you are trying to maintain or lose some weight. I learned in 2011 that I needed to log every workout and every bite of food. I lost .5/week over the course of 9 months and could not have done this without logging. For many of us that are active if we don't log our workouts and our food we're actually operating at too great of a calorie deficit each day (and not losing an ounce of weight). For example, to lose .5/week I have to eat 1460 calories/day NET. That means if I burn 500 calories doing Zumba I actually NEED to eat 1960 on that day to meet my goals. Sounds weird right? It did to me until I realized you have to fuel that engine in order to lose any weight. If I wanted to lose 1lb/week I would need to NET 1260/day during every single day of that week.
It sounds like a lot to digest (pun intended) but I wanted a free app to take the thinking out of it. I downloaded MyFitnessPal for free and really started to enjoy the process. It even has a bar-code scanner to log your food. I really love the reports to track my nutrition and exercise. So yes, I'm that girl that scans my organic milk and Kashi bar codes or oatmeal or eggs and sausage as I start my day.
If you're not into the logging check out Polar products--you don't have to log to see your progress. It's a fun gadget to include in your weekly routine. You might even find you get a little bit hooked on doing so...there's something so gratifying about actually seeing what you are doing during that hour you are sweating at the gym (or at home playing Wii).
What sort of tracking do you do? Do you keep a journal of what you do for activity or food? Sometimes if you see a nutritionist they ask you to track. I say put down the pen and paper and use a free website or app. It makes life much easier and helps me to meet my goals without added stress.