updated 01:35 pm EDT, Fri April 25, 2014
Technology so far limited to one iPhone model
Apple appears ready to bring Touch ID fingerprint sensors to the iPad Air and/or iPad mini, code in iOS 7.1's Touch ID framework suggests. Device identifiers tied to Apple's "BiometricKit" now include not just the iPhone -- prefixed with a 1 -- but the iPad lineup, prefixed by a 2. Because the identifiers aren't specific enough, it's not clear whether both the Air and the Mini will make the switch, assuming the code isn't premature.
Touch ID has so far been limited to just one product, the iPhone 5s. Apple has never said why, but may have been influenced by design costs and manufacturing scales. A Touch ID sensor requires its own complex circuity and software support, as well as a protective sapphire layer, which is costly to produce.