So you want to play around with your own smartwatch? CulBox has you covered. It is an open source wristwatch for Arduino with Bluetooth and sensors. Designed for Arduino makers, the watch has a 6-axis motion sensor, microphone, 3 push buttons, a piezo speaker, battery, and everything you need to get started.
You can build apps for the device without using Xcode or the Android SDK. The device has a 1.5″ OLED display. More info is available here.