A few months ago I posted about a music festival beacon that I created to help my friends find me in the crowds. After going to 2 music festivals with it, I am happy to report that it is a success! My friends were able to see me in very large crowds as long as it was dark out. I attached the device onto a tent pole to allow for hands-free use and to make it even higher in the air.
For proof of how visible a simple light-up ping pong ball is, check out this animation I made from a couple of photos I took of the screen at one of the performances. The camera was looking at the crowd from behind. That color changing dot is the beacon!