We’ve reported about the Teradek cube before. It’s almost a “cube” with a hotshoe below it so you can mount it on your camera and stream hdmi directly to your iPad or another network capable device.
In this video the Cube people show how it works as a directors wireless field monitor. Great, and at $1199 a great affordable deal. However there is a lag, so you should be careful about using it as a monitoring device to control focus or your camera.
With the new firmware update the device now won’t cause trouble on hdmi switching cameras like the 5D or T2i.