Sony Ericsson just announced LiveView - it's small, can be worn as a watch and it gives you access to the basic functions of your Android phone, while it's also highly customizable.
The Sony Ericsson LiveView measures 35x35x11 mm, weighs 15 grams and comes with a clip or better yet, a wrist strap so you can wear it as a watch.
The screen on the LiveView is an OLED unit - it's a 1.3 inches big screen with 128x128 pixels resolution. The screen is touchable - it has four touch-sensitive areas. The battery should last 4 days of normal usage. That probably doesn't include keeping the screen on all the time but still.
It's wearable and wireless. And you can customise it with applications.