Thanks for the tips all,
I'm glad to hear that it is a traditional practice (or at least based on one) - I try to strike a balance in all my music between traditional playing and innovation and particularly in coongas where the tradition is very deep. The fixing of the shaker to the wrist seems like a good idea since it enavles playing with both hands - I'm planning to investigate it later.
Another (silly) idea for egg shakers involves their eminently throwable nature. If you can learn to juggle them I think it could sound quite good. I can only juggle two

but you get both the continuous shaking noise as they flies through the air and the sharper noise as you catch them. My band is planning to have a (long!!!!) percussion section in one of our songs and the theory was that we could throw egg shakers to each other at various times (we actually own two each but throwing is more fun). I know its showmanship, I know its trivial but its fun and people love it.
Fish