Here's a short little video to demonstrate how the transmitter can trigger both a flash and a second camera. The camera on the left has a transmitter that fires the flash on the left and the camera on the right. The camera on the right, has a transmitter that fires the flash on the right and the camera on the left. The camera on the left is a Nikon D80. The camera on the right is a Nikon D70s. Both cameras are set to a 2 second timer. Unfortunately, the D70s' timer resets to normal shooting mode after it fires, so we see the D80 on a 2 second delay, then fires and triggers the 2 second delay on the D70s. When the D70s shutter finally trips, it triggers another 2 second delay on the D80. Since the D70s has now reverted back to normal shooting, when the D80 shutter trips the second time, the D70s gets fired almost simultaneously. If I'd had another D80, then the cameras would have just gone back and forth until I turned one of the shutter trigger receivers off, kind of like a cheap intervalometer.
It also appears I omitted the heading for the section on using the shutter trigger and flash trigger functions at the same time. So, I added it in the original review and expanded it a little. Here is a little clarification.
Using it as both shutter and flash trigger
You can use the RF-602 as both shutter and flash trigger at the same time. However, because there is a slight delay between when the shutter signal is fired and the shutter itself actually triggers, you cannot use one transmitter to fire both the shutter and flash at the same time. To do this, you need to transmitters and at least two receivers. Place one transmitter/receiver pair on one channel and use then to trigger the shutter as described in the previous review. Put the remaining transmitter and receivers on another channel and use them to fire flashes as described in the previous review. I had no problems doing this, there was no interference between the two transmitters, and it did not affect my flash sync speed.