This is a magic trick that lets you appear to telepathically impart your phones lock code to a random stranger.

Imagine walking up to a group of people and asking if three individuals could help with an experiment of the mind. You tell them that you need one volunteer among the three that is on the same wavelength, so to find a possible candidate you have each of the three spectators touch one of your outstretched five fingers.

Once done you inform one of them that they are perfect for the final portion of the effect. You now turn on your phone and reveal the password screen. You hand the phone to one of the three that did not pass the previous test. They are asked to input any four numbers and as expected they fail. The next volunteer is asked to do the same and again they fail.

Each time the login fails your phone displays a message informing them they have used up one of three tries and then the phone will be wiped. You approach the third and final person and ask them to clear their thoughts and listen to your voice in their mind. You hand them the phone and instruct them to enter the first four digits that come to mind. They do so and the phone is unlocked.

The same effect works on tablets as well.

Note, when installed the app is named Calculator. It looks like a normal Calculator app to avoid detection.