Although this is a video of a Nokia N800, which isn't even a smartphone, VMWare's MVP hypervisor virtual machine is enabling it to run both Windows and Android simultaneously. The virtual machine runs in the background of the native OS and allows a user to install different OSes as applications, then run them at the same time, if desired.
According to VMWare, the MVP is headed for smartphones sometime in the near future. The challenge they may face is the fact that they must partner with smartphone manufacturers and persuade them to install hypervisor on their handsets in order for MVP to work. It's difficult to imagine handset manufacturers wanting to open their device to multiple OSes, but then again, it could expand market appeal without adding much cost, if any. Would you want a handset enabled to run several OSes?