The Tago Arc is a bracelet covered with a flexible E Ink display that can display any design you want, controlled from your mobile phone. It has no battery as it draws all power from the NFC chip. It can connect to any NFC enabled Android device (iOS connection is not possible as the iPhone 6 NFC chip is not open to third-party apps).

The Tago Arc is a successful crowd-funded device, and can still be ordered for $250 (lower than the final retail price after the campaign ends).

E Ink display info: 
Flexible curved E Ink