The Nyrius Aries Pro is just one of many consumer grade kits available to stream wireless hd video via HDMI. I have a few articles posted on this blog going back a few years ago, but with the recent popularity of Gimbal Stabilizers, these streaming video tools can really aid your production. Here's a great demo from Rod Guajardo [thanks Rod] on how they use the Nyrius Aries Pro kits.
Though many of the wireless kits on the market may look similar, the internal components differ slightly offering faster processors and more channels for less interference, less video lag, and greater range. Still if you're just planning to monitor from a camera without having to be tied down by wires, the Nyrius Aries Pro is an excellent kit (found here).
Nyrius Aries Pro Wireless HD Video Kit
[Update] It should be noted that these kits have no mounting options so you'll have to be creative. They also require power over USB which are very common these days, but only certain batteries with a high mAH rating should be used. You can see a list of compatible USB batteries and also some creative mounts used by the CMR Radian kits (found here).
Camera Motion Research [CMR] Radian Wireless Bundles