From Jason Job:
iWasHere is a geo-locational social networking message board. iWasHere allows you to create an augmented reality by enabling you to leave a message at a specific location which can then only be read at that location. You can write to a Public network that is readable and writable by everyone, or you can create your own private networks for just you and your friends.
Use iWasHere to leave a note for a friend at a bus stop, outside their work or in a park. Read or write reviews of stores and restaurants right outside their doors. Make a virtual community message board in your neighborhood. Hide directions to a secret party or a surprise proposal. Create a treasure hunt that uses virtual clues or do virtual geocaching. iWasHere can be whatever you want it to be. The only limit is your imagination!