I agree with Sarah - you can't go wrong with Polar. I have the F11 and I LOVE it. The chest strap is very comfortable, not restrictive at all. The F11 has a lot of features and is geared toward the fitness enthusiast. It allows you to enter your age, height, weight, and it performs a fitness test to estimate your VO2max, so it can calculate appropriate target heart rate zones for you. It provides calories burned, percent of calories from fat, max HR, and avg HR. It stores your last 12 workouts, and provides a weekly summary of your data (total time exercised, time in each HR zone, total calories burned, etc). I couldn't tell you if the calorie burn calculation is dead-on accurate - it probably isn't, but it's probably a very good approximation.