Little did I know of the abilities of so-called “tethering,” for I had never tried it myself.
In the photography realm, tethering is a term generally used to describe shooting while the camera is directly connected to a computer. Most often, it is used to instantly push the photos onto the computer so that they can be previewed or, in some extreme cases, immediately edited by someone else for review by an on-site art director and so forth.
So really, “wireless tethering” is a super oxymoron, but that's what they call it when you control your camera wirelessly or retrieve the photos in realtime wirelessly. Canon makes a device for this, and it retails for $800. I think you'd really have to need it to spend that much.
At least, that's what Jamie Carl thought, so he made his own. Basically, tethering nowadays is just a standard USB connection, the same connection that you use to download photos directly from the camera (if you ever do that). They actually make wireless USB extenders now, which basically just separate one end of a USB cable from the other using wireless technology. It works just like USB, for just about anything that talks through USB.
I'm not sure what the bandwidth is like, but for controlling your camera, you don't need much.
Jamie wanted to have wireless control of his camera because he was going to be riding in a car at highway speed, with his Nikon dangling outside on a mounting bracket! It seems like it worked out pretty well!
Check it out on Jamie Carl's blog