-- Last Updated: Jul-18-08 5:43 PM EST --
I had investigated the laser signal as an alternative to flares, and couldn't make up my mind.
Signal flares are omnidirectional and have the advantage of getting the signal way up into the air (though only for a short period of time). They definately meet Coast-Guard requirements, but have to be replaced every 3 yrs, and can misfire.
It seems that with the laser you have to be fairly close and have direct lign-of-sight to the intended rescuer. If you were floating in the water with your PFD in waves of any significant height, the only thing you could reliably signal would be an aircraft. You might be able to time signals to boats from the wave crests. I'm not sure if the Coast Guard would accept the laser as an alternative to flares.
I personally don't like flares, but am not quite convinced to buy the laser.