I got one of the Motorola lapdocks for $50. They were meant to adapt an Android phone (Atrix or Bionic) to a laptop form factor, but with micro HDMI and USB keyboard/trackpad they're popular accessories for the Raspberry Pi. But they can also be used as just an HDMI display, either as a second monitor or with something like a Chromecast, Roku, etc.
This definitely seems like the most efficient route to go -- a LapDock for the Atrix runs $100, and every commercial alternative here is far more expensive.
Only shame is that the Lapdock 100 is unusable for it.
Only shame is that the Lapdock 100 is unusable for it.