Note: I created this tutorial last Sunday, sitting cross-legged on my bed, taking one-handed photos with my phone, all with anywhere from 1 to 3 cats within arms-reach at all times. (Cat-proximity is not relevant to the project but, I just thought you should know.)
This is a way to power some LED necklaces with a less-bulky battery pack. This needle felted battery holder attaches at the back of the necklace, which also makes it easy to have a light-up jewelry piece that only turns on when it's clasped.
If you are as excited about the possibilities of mixing needle felting, the most addictive fiber art on the planet, and soft circuitry, here's a nice little exploration