Touch ID is still a new technology from Apple, but that does not stop Cupertino consider may avenues in the future. While it seems logical to integrate the biometric sensor soon to iPad, a patent of Cupertino suggests that technology could actually be deported on accessories to attach to our iDevices as a sound or headphone doing USB.
Touch ID iPad and MacsThe patent describes very precisely how these accessories may interact with future iPhone or iPad, or even Macs (even if they are not reported in the patent) to the extent that a USB Touch ID could well fact be related to any Mac, to verify the identity of the user. As Apple has made a habit of patent by another, the iPad is here, perhaps one of the customary false tracks from Apple.
Such an accessory would make sense, especially in a professional setting where data security remains a key principle. The merge of iOS and OS X might facilitate the passage of Touch ID to the OS 'desktop' of Apple.
See also: iOS 8 beta 5 features explained. and What Apple needs to include in iOS 9: Maps, Humanize Siri and more.