This is a 60-LED circuit board watch we've developed that uses the same MCU as the Arduino Zero (SAMD21)!
We utilized the Arduino Zero early on in our development, and we feel this is a cool example where you go when you take your Arduino prototypes and squeeze them into custom PCBs.
We have an in-progress kickstarter project in order to make a big production run to get the costs down to a reasonable level.
Additionally, we're going to be continually updating a blog at http://blog.decko.us which will detail a lot of the different aspects that went into the development of this including accelerometers, light sensors, low-power, and various capabilities of the SAMD21. We hope a lot of these posts will help inform other arduino hackers out there.