The Yellow Arrow Project is coined a "global public art project" by its creators, but it's more than just that. It's a tagging of the physical world through mobile technology. How does it work?
"Participants place arrows to draw attention to different locations and objects - a favorite view of the city, an odd fi re hydrant, the local bar. By sending a text-message (SMS) from a mobile phone to the Yellow Arrow number beginning with the arrow's unique code, Yellow Arrow authors essentially save a thought on the spot where they place their sticker."
The above image is an example of one of the stickers. Visit the Yellow Arrow Project site to order your own stickers, or a shirt with a unique code that operates in the same way.