Have to admit the LED wristbands worn by the Sharks fans are way cool. Except if I watch them too long I feel like I'm getting ready to have a seizure.
I still have a couple I think from previous years. Just need some new batteries. Silicon with "bump" for LED/battery area. (Think like an elongated watch shape)
They are under "radio" control and have some really neat features (multiple LED light so they have a good range of colors that can be created). When not under control, they react to movement (e.g., clapping).
The first few games (2-3 seasons ago) they were passed out upon entry and randomly assigned to groups based on when bracelet was turned on. For later games, they laid out the bracelets by location (rows and/or sections) so they could do a number of patterns.