There is no better way to learn electronics than building your own robots and smart wearables. This guy has shared a guide that shows you how to build a Windows 98 wristwatch powered by Raspberry Pi A+. Windows is simply emulated on the Pi unit. You will need a case, buttons, battery, Powerboost 500, touchscreen display, and a few other parts to get started.
QEM, open source emulator, is used to complete this project. More info is available here. What do you think? Worth a shot?