OK, so I finally have them - radio transmitter which triggers my off-camera flash. So far, I triggered it with my built in flash, but there were some disadvantages:
1. Every time the built-in flash needed to flash, thus battery consumption was high.
2. When I didn't want the built-in to be visible in the shot, I needed to cover it with my hand, not very convenient
3. The off-camera flash was limited to 1/4 power only (p-ttl problems)
4. Both camera and off-strobe needed to 'see' each other.
Now, all those problems are long gone - once you have those wireless radio controllers, you won't even think about going back.
