Last night I checked out Pulse Park, in Madison Square Park. It's an interactive art piece by Rafael Lozano-Hemmer and it's pretty cool.
Observers place their hands on a pair of sensors (like you'd find on a machine at the gym), and then 200 ETC Source 4 luminaires pulse to the person's heartbeat:
(You can hear the generator loading down on each pulse).
When the audience member lets go, their heartbeat is added to the previous 200, and they sequence on one at a time and then mix together:
It runs until November 17th, stop by and see it if you can!