(Please tell me if this discussion does not belong here)
I think I may be starting to understand this stuff (a little bit).
Going with the photo I posted of the Arduino flash setup, there is a 220 ohm resistor between the Arduino pin and the optoisolator. If I understand it correctly, it's there because the pin voltage is about 5v and that would be too much for the isolator. The resistor brings the voltage down to about 1v (give or take) which then closes the circuit and causes the flash to fire.
So, if that's the case, I just need to get an optoisolator, find out what the input voltage needs to be, put an appropriately sized resistor in between the pins... and Bob's yer uncle.
How close am I? 
Thank you,
Carlo.