"Upon the launch of the iPhone 4, Jobs promised that Apple would immediately start working with standards bodies to make the FaceTime protocol an "open standard." As of November 2012, it is not yet known to have been ratified by any standards body, and the extent of work by Apple with regard to this promise is unclear as Apple has not released technical specifications for the service. FaceTime is not currently supported on any non-Apple devices."
http://en.wikipedia.org/wiki/FaceTime