Quinn Dunki made this “beating heart” LED pendant using the “Pulsing Glow” circuit experiment from the Make: Electronics book. She writes:

While reading through Charles Platt’s excellent book Make: Electronics, I came across this nice little circuit for making a gentle pulsing LED. I built it for fun, and was struck by the “humanness” of the pulse, but couldn’t figure out what to do with it. Later I found a heart-shaped tag on some pants I had bought, and well, this is the result. I opted to use mainly scrap parts salvaged from various sources. I liked the hacky recycled feel that gave it.

I took Charles’ circuit, and added a second LED for some symmetry. The bob under the pendant is the power source. The pendant’s chain is part of the circuit, so the clasp becomes the on-off switch.

[via Make: Online]