This was one of my first Arduino projects. After some near misses with bicyclists while running at night, I decided to get some lights so people could see me in the dark. But why stop at boring plain lights? Wouldn’t it be cool if they could respond to my heart rate?
I looked at a number of existing heart rate sensors for Arduino, but most were optical and could not get accurate readings while I was running since they were constantly being jarred. Since I run with a Garmin GPS watch and heart rate monitor, I tried to hack into the information being sent between the heart rate monitor and the Garmin watch.