Wearable electronics is commonly used in many areas. We are not talking about professional stuff like medical devices, but more hobby corner. But who knows where is a limit. Today anyone can assemble wearable projects with cheap building blocks that are mostly based on Arduino. AwesomePCB have shared his instructable on how to build a wearable OLED display covered with leather frame that blends pretty well on fabric.
He used small SSD1306 128×64 OLED display which is connected to small Attiny85 Arduino compatible board. Coin cell battery is enough to power it for quite some time. He paid some attention to details on how display is attached to leather piece and how this piece is snapped to clothes. You can do many fun stuff with the display including a temperature monitoring by attaching thermometer, it simply do rudimentary activity tracker with accelerometer or display current your mood with smileys which can be changed with single button press.
We recommend EasyEDA for circuit design and PCB prototype