Also if you use profoto flashes (not compacts) they can trigger on IR signals, this means you can attach a Canon (don't know about Nikon) wireless transmitter on top of any camera with a flash shoe and remotely trigger the flashes. There has to be a line of sight between the pro and camera, and you may find that you have to angle the pro-power pack towards the camera position.
In order for this to work, all contacts except the large trigger on the bottom of the canon have to be isolated with electricians tape, if not the Canon device transmits a small "measure the flash" IR beam, causing the pro-packs to be triggered before the actual exposure is made...
I have used this as a backup once when my pocketwizards ran out of juice.
-axel