Yarn Yardage app for iPhone and iPad

Ensure your device is equipped with magnetometer.
Mount a magnet (e.g. fridge magnet) on the end of one of your Swifts shoulders bottom side.
Measure the length of one loop of your Swift and type in the value in meters or yards. Note that corresponding unit (yard or meter) will be updated automatically. You need to do it only once. When you open the app next time the loop length will be recalled from the apps memory. If you use a different Swift, the loop length value needs to be updated.
Place your device with the Yarn Yardage app under the swift so that when it rotates the magnet goes above the device .
Turn the shoulder with the magnet away from the device.
Press "START" and start rotations. Each rotation will be detected by the app and loops, meters, yards numbers will be updated on the app screen.
When done measuring the yarn yardage, press "STOP". This does not clear the calculated number of meters/yards. The number of meters/yards is cleared when start is pressed again.
It is possible to continue counting after "STOP" is pressed. You can start without resetting measured yarn values by selecting "Without RESET".
You can view the history of measurement sessions. The History button is added below the Instructions button.
Button f(x) opens a calculation section with helpful calculation functions. Proportion and yarn length calculations are available.