This app allows you to measure the approximate length by moving your iPhone.
Tap [Ready?] button to start measurement.
Move your iPhone toward the home button.
It calculates the moving distance from y-axis acceleration.
Hit a cushion or the other hand to finish measurement.
Time, angle, and distance of recent 6 measurements are displayed.
YouTube Video :
https://www.youtube.com/watch?v=51wkPDQpKF8