The M500 GSM Watch from Australia isn't your only cellphone watch option now with the Cect Mobile watch from China. It's got a semi-decently large LCD, six hardware buttons, GSM support, Bluetooth, MP3, MP4, FM radio and a headset jack. No pricing yet, but it does come in all sorts of colors. [Phone Daily via Slashphone]
Ya know, If I recall right, Siemens came out with a phone about 5 or 6 years ago called the SL55. It was a really tiny slider and with a wristband and a little velcro, you could accomplish the same thing. Plus you would get a web browser and a full keypad.