Hi lately I have been thinking about trying to build a way of finding your friends when you are in a big crowd at music festivals. Everyone's phones typically die within the first day or so, so I was thinking about using two GEMMA (https://www.adafruit.com/products/1222?&main_page=product_info&products_id=1222) arduinos to communicate their position to each other. I currently have a gemma with 24 RGB LED's arranged around it. I figured if I could get the direction from the other gemma then I could light up the LED that corresponds to their direction and have the brightness correspond to their direction.
If anyone could give me some direction of the communication portion of the project that would be really helpful. I would like the communication distance to be about 200 acres or as large as possible.
Thanks in advance.