Ben, I had a flood last year with my MMII-EX after about 200 total dives. It was my fault, I assume, I probably got lax on maitenance after 2 straight weeks of diving. Fortunately the flood was minor (the system was repairable and the repairs were about $50 total) but it did cut short my photography for the trip.
I have not considered getting a moisture alarm for the Ikelite housing but from my initial impressions and tub testing I find that checking the o-rings on the housing is quite easy due to the clear nature of the housing. If the o-rings look right then they probably are right.
Still, I would recommend practicing assembling the system and putting it a tub a few times without the camera (this is what I have done to get comfortable with it). I also plan on taking it on a few pool dives before I get it out into the ocean to develop a level of comfort with the system.
That said, the Aquatica Universal Moisture Alarm does sound intriguing and I would love to hear from people who use them in the Ikelite housings.
Craig