Heart Beat Rate Pro (US$1.99) represents one of a new breed of iOS apps that measures your pulse using the iPhone's built-in camera. It works by holding your finger over the camera. With the built-in flash illuminated, the app counts your heart beats, automatically detecting your pulse.
I tested the app on several subjects, simultaneously using a pulse oximeter reading for comparison. What I found was that for casual use, the app did a pretty good job, all things considered. There were, however, drawbacks compared to the pulseox.
First, it took a lot longer to sync the signal. The fingertip unit could pick up a pulse in just a few seconds. The app took nearly a minute of synchronization and measurement. And, there were times when the app failed to sync, so couldn't measure the pulse at all.
Second, the app was a lot less accurate moment-to-moment. Although the results were pretty good on average, the immediate measurements were sometimes off by a bit. The results improved over time, as the sync grew steadier.
The values towards the end of each minute's trial were better than the ones at the start. For example, on one trial, I got a reading of the low 50s on a pulse that was actually in the 90s. It caught up by the end of the trial.
Finally, I found that there's a bit of a trick on using the app. You need to have the subject hold the phone with one hand, placing his or her finger over the camera hole. Reversing this position provided insufficient coverage over the camera.
In the end, this is a nice little app for runners and anyone else who does exercise. If you don't like standing with your finger over your wrist, counting while watching a second hand, it offers a workable alternative.
For those who are really serious about self-monitoring, you might want to pick up a normal athlete's monitoring system or buy a pocket pulseox unit instead.