anyone own a "water wiggler?"

hi,

i have seen these devices advertised. they supposedley lightly agitate the
water in birdbaths thus preventing mosquitoes from laying eggs and also
attracting birds through the motion of the water.

i did a group search and while they are mentioned on occasion, i can't find
anything where someone says, "i have one and they are good, bad or
indiferent."

does anybody actually have one of these devices in their birdbath that would
care to elaborate on it?

thanks,

mike