Kevin Rye built this E-Paper clock and wrote a detailed explanation on his blog describing the build:
I still have to put the finishing touches on the code. Instead of having the display constantly update, I’d like to set an alarm on the DS3231 RTC to go off once a minute, and only update the display on alarm. Hopefully I’ll save some battery power that way. As of now, the battery only lasts a couple of days. I built in a USB battery charger to make it easier to charge it. I got my PCBs in from OSHPark and put it all together in an 80mm x 80mm Sick of Beige case. Check it out!
Via the forum.