They could be used to read minds, control them, and add information into them (news or a daily joke, for example). They were also the alternate universe's alternative to iPods, mobile phones and music players. During their attempted conquest of the Doctor's version of Earth in 1851, the Cybermen made cruder versions of the EarPods to control four workhouse owners. When the workhouse owners were no longer of use to the Cybermen, Miss Hartigan activated a switch which caused their EarPods to electrocute and kill them. (TV: The Next Doctor)