Shekinah on here has done that before. She's got a video where she just put like two sparklers on a hoop and it looked really cool. Especially when she was doing the vortex. Here's the video—the sparklers are at 1:45.
Ahhhh.. that's me! lol. Ya, I just bent the wire of the sparklers around the hoop a bit and taped them on. You can see a clip of me putting the sparklers on in this video the first time I tried sparkler hooping- http://www.youtube.com/watch?v=3e8dq3bF-80 You can do many more than 2.. they just don't light well at all in the cold, so doing it now in the summer will produce much better results :)
The first sparkler video I saw was Kelsey.. she has some awesome sparklers that seem to throw sparkles all around her. Definitely not the dollar store ones I have - http://www.youtube.com/watch?v=PYcBUKEG9-I