An ideal signal device for kayakers?
Nate,
I don't think there is one, which is one reason why I try to carry several different visual signaling devices. As kayakers we are all limited by space, accessibility, utility (ease and ability to deploy), effectiveness, and costs these devices pose to one's wallet. On top of that some of these pyrotechnics are very difficult to find. If you try to mail-order them wait until you see the DOT HAZMAT shipping fee! That will put you in a state of emergency (i.e. heart attack).
As an aside the Boat.us reviews also stated the following on the often carried (by kayakers) Orion Skyblazers:
"testers felt that the directions were very small and not descriptive enough to feel confident that they were firing the flare properly. This was magnified because of the units’ small size—which also gave the impression of having more apparent recoil than the bulkier SOLAS models. Proper hand placement on the device is imperative—holding it improperly can lead to excessive recoil and potential injury."
You still have to use two hands to launch a Skyblazer and probably any other aerial flare out there with the exception of a flare gun. Even with that you would use two hands to load. If out of my boat I would try jamming one leg in the cockpit while floating on my back. It would free both of my hands for flare deployment/launching. You are right it's not nearly as easy as doing it from the deck of a large ship.
I guess we get to pick our poison(s). I certainly do not have a one size fits all answer.