TshirtOS, while looking like an elaborate hoax when we last reported on it, really is an actual concept. It's a t-shirt running an operating system and offering more than your current t-shirt could.
...of Windows 10, more Windows 10, and some other stuff
Windows 10 review: Microsoft goes back to the future
Windows 10 'Service Release 1' coming this month
These ten Lumias will be first to get Windows 10 Mobile
The Redmond Report - Episode 4: Windows 10 gets hit by lightning