Cybus EarPod

EarPods were devices from a parallel universe, created by John Lumic.

History
They could be used to read minds, control them, and add information into them (a daily joke, for example). They also took the place of mobile phones and music players. They were used as the alternate universe's alternative to iPods.

Secretly, however, Earpods could remove information from a subject's brain by producing two metal prongs that met at the top of the head. (DW: Rise of the Cybermen) EarPods were used to induce trance prior to "upgrading" of Humans into Cybermen. the Earpods took control of people by inducing a trance but on our Earth the earpieces were drilled straight into the victims brain. (DW: The Age of Steel)

When the Cybermen entered this universe, the earpieces of the Torchwood Institute, specifically, Torchwood 1, allowed control in a similar way, paving the way for the Battle of Canary Wharf. Adeola Oshodi died as an indirect result of this. (DW: Army of Ghosts)

During their attempted conquest of the Doctor's version of Earth in 1851, the Cybermen made cruder versions of the Earpods in order to gain control of four workhouse owners. (DW: The Next Doctor)

Other information
EarPods also exist as a source of private entertainment on the Doctor's Earth. (BFA: Cuddlesome)

There was some discrepancy in their initial appearance as to whether the EarPods were surgically grafted on and therefore permanent or simply plugged into the ear like a real-world Bluetooth headset. In DW: Rise of the Cybermen, Jackie shows off the new EarPods she received from Lumic and mentions them having been grafted on; in the subsequent episode, however, Pete is shown to take them off with ease after The Doctor warns him that Lumic might take advantage of its presence.

Behind the scenes

 * The name EarPod fairly obviously takes its inspirations from iPod.