HRM Help!

Since I've started MFP, I've noticed that the calorie counts don't always seem to be right on here for exercise. For instance, my husband and I run and walk a 3.25 mile loop about 4-5 times per week, but it's slightly uphill, and on some days I'm running into the wind, not to mention pushing a jogging stroller with my 20 month old. There's no way for MFP to compensate for that. So, I recently purchased a Mio Classic HRM mostly because it was on clearance because the store was not going to carry the pink model anymore. I figured an HRM is an HRM, and I liked that it was a strapless one. The problem is that it wouldn't consistently take my heart rate while I was running. It was fine while I was walking, but sometimes I had to try five or six times to get a reading while running, and sometimes it was an off the wall reading like 60 bpm while increasing speed. Needless to say, I took it back, but now I'm on the hunt for a different one. I really don't know much about them, and I want to get something I'll be happy with. I'm not against wearing one with a strap as long as it's comfortable. I also have small wrists, so I need one that has a small watch band. I'm mainly looking for one that will give me calorie burn, show my fat burn zone, and record the length of a workout. I don't need anything fancy, just reliable. I've read so many mixed reviews on different HRM's that I'm absolutely lost. Right now I'm leaning towards a Polar FT7F. I would like something for under $150 as well. I'd love to hear feedback, especially from fellow runners!