App for verifying the magnetic poles:
The app helps you find the North and South poles of magnets. Approach the magnet to the phone's sensor. The phone's screen will turn into red or blue, according to the direction of the magnetic field. N shows the North pole and S the South pole.
Red : North pole
Blue: South pole
Keep the phone in a horizontal position. Rotate the phone until the red end of the magnetic needle points to the letter "N". This is the North direction. The letter "S" points to South.