That would be my thinking. A Google of "ir heart rate sensor" will get you a dozen or more hits. These sensors are very inexpensive and easily interface to micro-controllers and other displays. A complete sensor unit, including the LED emitter cost about $3.50 USD. These are what is inside the little clip on units you see used in hospitals or anywhere a heart rate is measured.Forgive me i f this is irrelavent, finger pulse detectors are usually infra red, such a circuit would be easier to build.
The original post was in 2009. Maybe MEMS accelerometers were not so easy to find back then? I could not say as I don't remembersam288,
You'll need a very sensitive accelerometer to detect this (obviously) but even then a piezoelectric accelerometer may not be the best option. Our heart rate should be roughly 60 beats a minute or on the order of 1 Hz which is at the lower end of piezoelectric accelerometer's bandwidth. You may be better off with a capacitive MEMS accelerometer or piezoresistive.
Here's a link on some basics of accelerometer selection and the difference between the three main accelerometer types (piezoelectric, piezoresistive, and capacitive MEMS): http://blog.mide.com/accelerometer-selection