The first thing that caught our attention to the new Misfit Ray is how small this activity tracker is. At 1.5″ in length and only 0.5″ in diameter, this little tube houses all the electronics plus the batteries to power the bluetooth radio, 3-axis accelerometer, multicolor LED display, and the piezoelectric vibration. What’s interesting is Misfit’s choice not to use rechargeable batteries. Instead, they opted for the standard 393 button cells you can find at most grocery stores in the US. That choice of battery means that you don’t ever need to recharge the Misfit Ray – thus no need for a connector (which makes sense for a water resistant device) or a recharging circuit (where to put it anyway?). The length is for the most part driven by the average size of a person’s wrist: make it a bit too long and the Misfit Ray will look awkward around your wrist. You can fix that by making the device curve to follow the line of your wrist, but that makes things much more complicated. The cylindric design choice makes to an easy to mechanically fabricated and assembly device – but makes the electronics very challenging! See it for yourself in the following video. Note how the talented engineers at Misfit had to fully utilize the roughy 1/2 inch allocated for the electronics in 3 dimensions. To accomplish that they designed a mezzanine card that sits right on top of the main board. Both boards are connected via a flexible circuit. We extracted the rotation video as a gif so you can appreciated the work of art done by our fellow engineers at Misfit!