Hi Bicky51, welcome to the forum.
Thanks for the link, (already posted here: http://www.ausrocketry.com/forum/viewtopic.php?t=1011
There are definitely some very cool little mechanisms there. I already have my eye on the batteries that they use for these planes. They would be perfect for water rockets (or pyro rockets) as they are small, super lightweight, can be easily recharged and carry enough power to drive servo motors and everything else during flight.
Two of these weigh only 6.4grams and can deliver 1.6A for a few minutes. We currently use 2 x CR123As which have a combined weight of 32 grams. We need two to get enough voltage.
Compare that to a 9V battery that weighs around 46 grams.