Echo is a pseudo-anonymous, location-based picture sharing app. Take a picture, scribble on it, and upload it as an Echo. Once uploaded anyone in your immediate vicinity will be able to view your Echo. Use the map to find Echoes in your area.
Echoes have a limited range. When you enter an echo's range, the echo icon will change from red to green. When this happens you can click the Echo to open it, but be warned once opened, Echoes will disappear forever.