CPSCockpit simulates a standard single engine aircraft VFR Cockpit using the iPhone GPS receiver.
It simulates speedmeter, altimeter, course indicator, climb indicator, experimental turn coordinator, g-meter and position information.
As with all GPS applications, CPSCockpit needs a direct view to the sky, the less obstacles are in the way, the better it works.
Movement in a general direction is needed for course, speed, climb, and turn indicators. Faster movement leads to a better result.
It usually takes some time to get a good GPS Fix, even under clear skies.

Although I work hard on not unnecessarily using GPS in the Background, here's the disclaimer:
Continued use of GPS running in the background can dramatically decrease battery life.