The Pulse Sensor Amped, made by pulsesensor.com and sold at Adafruit.com, is a wonderful bio sensor. With the sensor and an Arduino, some very interesting projects can be made.
The examples of using this sensor (on the pulsesensor.com website) start with a blinking single color LED and rapidly go into examples interacting with Processing and other computers.
This leaves room for a very interesting application: using the pulse sensor values to vary addressable LEDs such as Adafruit's NeoPixels. From a single pixel to circles (or a heart shaped design), to a costume full of pixels, people will know when your heart is racing!
This project is inspired by and designed with Laura Barela.