Is Facebook secretly building a phone?

So what, exactly, is this superteam of designers, engineers and manufacturing experts working on? Nobody outside of Menlo Park knows for sure, but the hires -- and at least one under-the-radar acquisition -- seem to indicate two things: it's mobile, and it may be modular.

All of Facebook's new expertise could go towards anything else that uses mobile processors, radios and the Android OS -- such as headsets, tablets, watches, smart home and other internet-of-things devices. Or something entirely new.