I have been to an event last night, where I some wristbands produced by the Crowdled company (see links at the end).
Material of one band: 3 colored leds (2 in total) and a button. Runs on battery. For the pictures I opened the bands (2 screws). In the middle of the IC the code FL27.138 ist labeled. The rest of the band which is not visible in the pictures is only plastic.
Functionality: once I reveived the band, the button changed color and turned the leds on an off. Later a radio controller controlled the leds, the button couldn't even turn the leds off. (Range: about 750 metres, regarding the website of the producer). One day later, at home, the bands do not turn on at all, even those which haven't been activated at the event (plastic seal at battery was attached). EDIT: The bands work like when I received them. The problem was empty batteries.
Question (EDIT): How can I reuse the bands? Probably the radio contoller consumes energy for the whole time, which empties the battery's within a day. Any idea how to disable the controller?
Links and further information: producer: https://www.crowdled.net/how-does-it-work/ similar hacks for other bands: http://www.instructables.com/id/Hack-Your-Xyloband/ and https://www.youtube.com/watch?v=UQHpJ0dJJXQ