This is a simple electronic compass and speedometer ideal for use in your car or boat. It uses the iPhone GPS to determine heading and speed and displays in either metric or US units.nnNote: As with ANY gps based compass, you must be moving for direction of travel to be computed as it is based upon change in position coordinates.nnALSO: This obviously requires a GPS so this won't work on first generation iPhone or the iPod Touch.nnLarge easy to read numeric display of speed.nnDual mode scale:nScale rotates with heading at the 12 o'clock position.nOr, scale is "North up" with a heading arrow that rotates around the scale.nnUS or Metric units dynamically selectable: Miles per hour, Kilometers per hour, Knots.nnReadout of current latlon in the lower left of the screen.nnPulsing "star" confirms GPS update activity.nnHUD Heads Up Display mode inverts scale so it reflects properly off your windshield when placed on dash at night. It's cool to be able to view your speed and direction without taking your eyes off the road.