Cardiograph is a universal app that purports to measure your heart rate via the cameras built into the iPhone or iPad 2. The app has a very slick-looking user interface reminiscent of a real-world electrocardiogram, complete with authentic (and irritating) sound effects, including the always-unnerving sound of a flatline.
The app functions similarly to a pulse oximeter, measuring blood flow through a finger placed over the camera and converting that into a pulse rate. Cardiograph has support for multiple profiles and can keep track of multiple users' heart rates over time -- if you can get it to work, that is.
Unfortunately, I found Cardiograph was very twitchy about properly measuring my heart rate on the iPhone 4, and it didn't work at all on my iPad 2. On the iPhone, the pulse rate seemed to jump wildly between 100 and 0 beats per minute -- my actual resting heart rate is usually between 45-50 BPM -- while on the iPad 2 Cardiograph insisted it was too dark to obtain a good reading even though I was in a well-lit room and holding my finger right in front of a light.
Given Cardiograph's visual polish, it's unfortunate that the basic function the app is supposed to fulfill works so poorly. It's not as though it's impossible for an app like this to work well; I've been successfully using Instant Heart Rate for months. While that app is still less reliable than a chest strap sensor (or even just taking your pulse the old-fashioned way with a finger and a stopwatch), Instant Heart Rate still manages to get an accurate reading much faster and more reliably than Cardiograph.
Actual heart rate at time of reading: 50 BPM
Cardiograph was just released and has a lot of potential, so hopefully developer MacroPinch can fine-tune the measuring capabilities of Cardiograph and get it to the point where the app is more usable. As it stands now, the 1.0 release of Cardiograph doesn't function well enough for me to recommend it.