Some toughts about additional features.
Lisamith's idea in using the watch a desk-clock is pretty cool (and probably more usable usecase than the use as a watch). To use it like this it would be great if the watch could get it energy via usb and/or could be activated with a motion sensor.
If the watch is getting it's power via USB connection, the display is always on. If there is no power via USB, the display goes off, but the clock keeps the time over the battery.
If this is not possible, the clock would need a short range movement sensor, since you would otherwise have to take the clock in your hand each time, you want to display the time because you have to press a button on the clock.