I finally dug into the 7D manual to learn about the new built-in wireless flash feature. I was worried it was going to require one of the newer flashes. That would be a bummer for me since I am still using two beat-up Canon 550 EX flashes. But they get the job done for me so I am in no hurry to replace them. So I was very happy to discover that the EOS 7D's built-in wireless flash feature will work with any Canon flash that's equipped with Canon's infared wireless functionality. To use the new wireless flash system, you go into the camera menu to activate and setup the wireless flash. Then you set your flash to act as a slave, open up the 7D's pop-up flash and fire away. In the photo below I'm holding a 550 EX in my right hand and it's being triggered wirelessly via the 7D's pop-up flash. Flash metering is via the standard E-TTL system so you don't have to manually set the flash exposure as you would with a radio slave system.
I'm really excited about the 7D's wireless flash. It's been a long time coming for Canon - Nikon, Olympus and Pentax have offered it on DSLRs for quite a while now. It's going to be a godsend for me at tradeshows, parties and when I want to travel light in the backcountry. I'm glad I finally took the time to figure it out. And I'm really pleased that Canon didn't require me to buy a new flash to take advantage of it.