The patent, which was filed last week, describes tattooing, stamping or spraying 'ferromagnetic' material onto a user's skin and then pairing it with a mobile device. It says different vibrations could be used to create a range of alerts. It suggests a magnetic marking could be attached to either a user's arm, abdominal area, finger or fingernail.

The filing also suggests that the magnetised marking could be used as an identity check. It says that by picking a certain shape the user could create a 'specific magnetic impedance' - effectively their own magnetic fingerprint. It says this could act as a 'password" and gives the example of a laptop refusing to display content on its screen unless it verifies its user is close by.