Get well soon

Here is a use for one of the strange but inevitable results of modern society: singing greeting cards. The materials in one of those cards, plus a cheap resistor and capacitor, are enough to assemble a perfectly usable pulse sensor. The original paper suggests that this off-the-shelf solution could be used in an educational setting. 

A little Googling shows that a number of pulse sensors are available or can be made for all kinds of platforms.

• This one is intended for use with Arduino. Total cost is ~$25, not counting whatever it's attached to.
• For comparison, this one is a more clinical model. I can only imagine how much it costs.
• This setup uses an optical approach instead of a piezoelectric one. It seems like overkill, possibly because the signal requires a lot of amplification.

I'm imagining an art project in which a viewer's heart rate changes the intensity of lights in a room or turns certain appliances (i.e., a fan or a radio) on or off at certain rate thresholds. Even something like a cheap knock-off of this bike helmet seems entirely feasible.