Here are three of the light-emitting power rings from the GREEN LANTERN: BLACKEST NIGHT line, and I think they kick ass.
I shot this without a flash and did not tweak the colors, so you can see for yourself how nicely they glow.
I got them at the NY Comicon and found them quite reasonable at ten bucks a pop. Yeah, I know they're basically cheap hunks of plastic, but they are very well-made and look like the items as seen in the comics, so I actually expected the manufacturer to gouge collectors for at least $15-$20 per ring. And you know what? I bet the fanboys would have gladly paid that. I personally would have definitely spent as much for a Green Lantern Corps ring that lights up, and also for one from the Sinestro Corps. My one gripe is that the CR 927 Lithium battery that powers one of these rings does not pack much of a charge and dies out after perhaps a couple of hours of continuous activation, and unlike in the comics the wearer has no power battery to recite an oath over while recharging. Fortunately it's pretty simple to change the wee battery when needed.
Anyway, I'm betting we'll see a lot of these on Halloween as geeks of all shapes and sizes rock costumes from all of the different ring spectrums.