Developer: sportstracklive.com
Price: Free
HeartRate is a very simple app that calculates your heart rate using your Android’s touch screen.  By tapping the screen for about 15 seconds based on your pulse, it gives you an accurate reading of your Beats Per Minute.  Additionally, it will tell you what zone your BPMs are in based on your age.  The ability to display a real heart is a nice touch, and looks really cool when you tap it.  Furthermore, you view your history of readings, and name them, allowing to track your heart rate over time.  If you want to know your heart rate down to the beat, you can purchase a Zephyr HxM, and the app will read your heart rate using bluetooth, assuming your running Android 2.1.  However, this option is very pricey at $99.  HeartRate is great if you want to keep track of your heart rate after a run, or if you just want to know your heart rate.