Canon Have had an FEL function for many years starting with the T-90 film camera, you pressed a small button next to the shutter button and the camera pre flashed and stored the value, it worked quite well.
Back to the OP question. I assume you have seen this thread: http://wetpixel.com/forums/index.php?showtopic=62305 where it is established the buttons don't do as labelled, seems like it's just a TTL flash and as discussed here seems to be limited by the pulse time of the trigger. Basically it's an incompletely reverse engineered knock-off. The question is raised regarding the INON or Retra options and whether they suffer the same issues and the answer is no, they work, I've used TTL for macro shots and as long as the subject fills the frame they seem to work just fine, but if you try something like a nudi perched on a sponge with black water BG, it goes back to hit and miss, The only risk is whether the the TTL triggers will work, the flashes will be fine. The Retra is still not available for purchase as it's being re-developed, so that leaves INON. They have a good reputation and if the camera can work out the right exposure it will provide the required light.
As it stands your connection options are the non-TTL Nauticam triggers and Turtle offers a TTL option that either mounts in the hotshoe or separate cable to the hot-shoe. With a different housing there would be more options for example a wired TTL connection with an ikelite housing and ikelite strobes. The real question is how well the TTL trigger will work. The non TTL options are available now and I would expect they are reliable. The INON strobes have a very sensitive trigger so should not have any problems with the non-TTL triggers offered as long as the LEDS line up with the fibre optic ports on your housing.
