Anybody heard of "electroluminescent wire"?http://www.glowire.com/photo_gallery.htm has some stuff about it, but look for other companies and web pages about it on the Internet.
I've read that some can be run by a 9 volt battery. I suppose that wouldn't be too difficult to fit into a poi handle of sorts. The wire's fairly flexible, too.
Pricing is about what I'd expect for something fairly new, but not *too* bad. $11 bucks or so for a single four-foot section, then another $10-20 for a driver (battery-connector thingy...)
I saw a guy experimenting with neon strings as poi, at last year's Portland Juggling Festival. He had the batteries within tennis balls, and was actually swinging them around. He'd found that when the strings strike each other, that spot no longer lights up, so they were in plastic/rubberish tubes. Very clunky things, too, but mostly an experiment.
There was a "refresh" rate to the strings, also, which gave a funky sort of strobe effect. Doing one psychadelic-looking move, he said "People in Eugene WORSHIP this!"
I'm not sure, but I don't think his was the same as this wire. I don't know much else about the EL wire, though.