We just released version 1.2.3 with a couple of significant improvements. The most exciting improvement is the introduction of continuous adaptive auto-calibration, that does away with the 'Calibrate' button and delivers much better attitude indication in a range of situations. Just fly level, make sure the AI is level (tap the center) and in a few minutes the sensors will adjust to the current flight conditions (engine vibration, turbulence and temperature). This significantly reduces the precession that is caused by the automotive-grade gyro sensors and the hostile environment (engine vibration in particular is a difficult problem for a handheld gyro).
Other improvements include communication frequencies for the nearest field, a slip indicator (the small rectangle hanging off the upward-pointing triangle in the Attitude display), an automatic flight timer and an option to use GPS-derived attitude on devices that have gyro sensors.
Thanks for your interest in Flight Instruments, and don't hesitate to leave us feedback on your experience with the app, or suggestions for improvement.