Suggestions for a calories-burned tracker.

Research the Fitbit. I just got mine and am really liking it so far. It tracks your steps, miles, floors climbed, calories, activity level and even your sleep. It syncs with MFP for calories and activities and, once you get it setup right, is pretty accurate - I've been tracking it with my HRM during my workouts and it's only a little lower. I still use my HRM since the FB doesn't track heart rate and I know some of my workouts are intense so I don't want to miss any of those calories.

You can read more about it here: http://www.myfitnesspal.com/apps/show/fitbit (I got mine on Amazon for under $100).

Also, there's a great group that's got a lot of information: http://www.myfitnesspal.com/groups/home/1290-fitbit-users

Absolutely, when it comes to exercise - especially higher intensity exercises. But HRMs are not meant to be worn all day to track calories burned. If you get most of your workouts through the treadmill and lower impact workouts DVDs, it's probably not a big deal. But, like me, if you're doing high impact workouts (like Insanity, where your HR is very elevated) the HRM will factor that in, where the FB is tracking your elevated activity level and factors calories based on your weight (and probably few other things I'm not aware of - I don't know FB's algorithms).

Many people with FB still use their HRMs for workouts and then after they log the workouts, FB calculates the difference between that and their other daily activity and makes an adjustment to the exercise diary. That's the "Fitbit calorie adjustment" you might see in people's diaries. Mine have ranged from 30-300 per day, depending on my workouts and other movement throughout the day.