(via) Play Treasure Hunt is "a location based pervasive game for handheld devices, combining a clue driven Treasure Hunt with an action strategy Mech battle game.". It's based on GPS.

Treasure Hunt is a location based mobile phone game that uses GPS and internet enabled handhelds. We have hidden an imaginary treasure somewhere in your game zone and you must attempt using the clues we give you to try and find it. All players begin the game with one video or picture clue, and a number of multiple-choice answers, only one of which is the correct answer. Be careful when answering the clues, if you answer the clue incorrectly your next clue won’t be so helpful in your quest for the treasure, instead you might find yourself going in circles. (...) To find the treasure you must answer the clues. Use the clues you have received over time to piece together the puzzle, use these clues as a road map to find the location of the treasure. Its not that hard, we want you to win, just try and figure it out.