There are plenty of reasons why you may want to regularly check your heart rate. After a recent run, I wanted to compare the performance of: 

• Cardio Buddy 0.99$
• Instant Heart Rate 0.99$
• Wahoo ANT+ Heart Rate Monitor (Check belt and ANT+ key for iphone)  $99.00

The measurements were taken within seconds of each other so I could be sure nothing else could impact the results.

First up was Instant Heart Rate. To use this app, you gently plate your finger in front of the back camera & flash. After a couple of seconds, it detects and counts your heart rate.

Next up was Cardio Buddy. In addition to performing a useful function (calculating your heart rate), it also has a high cool factor in how it measures your heart rate. You frame your face (using the front facing camera) and it calculates your heart rate using blood flow variations not visible to the human eye. This is a cool party trick. Everyone I show this to is surprised and amazed.

Last was my trusty chest based heart rate monitor. I have previously compared it's results to those from my blood pressure monitor and they usually match.

Comparing all of the results, they are relatively close but Cardio Buddy seemed to be closer to the my chest based monitor than Instant HEart Rate (which surprised me). I ran another series of test 30, 60 and 90 minutes later and the results were a almost the same. As the rest period grew longer, Instant Heart rate got closer to the chest monitor but in all the tests, Cardio Buddy was the closest.

It is important to note that the 2 app based monitors are best used in an indoor or shady environment without harsh direct sunlight.