Apple TV (2007 to present)
Development status: Closed
Platform size: 3
The Apple TV digital media box began its life as a special-purpose x86-based computer running a modified version of OS X. In 2010, the platform fractured drastically, shifting to an ARM/iOS combination that more closely resembled an iPhone than a Mac.
So far, Apple’s diminutive TV box isn’t an open or even moderated platform, but with an app-like home screen in the most recent OS version, many suspect that that status will change at some point.