No it's not a Dick Tracy fantasy - it's reasonably priced, available now and there's an SDK for it.
Just when you though you had considered all the options for your killer app - there's a new platform in town. The inPulse digital watch is a programmable Bluetooth-connected "smart watch". It's just right to pair up with your smart phone, netbook or portable and it costs $149.
It can work in two ways:
A programmable display on your wrist
An alerting platform, connected to your smartphone (Android, Blackberry, Jailbroken iPhone) or PC (Mac OS X, Windows, Ubuntu).
An SDK provides pixel-level control of the display and access to Bluetooth messages. The connection isn't full Bluetooth, it is described as "blue-flavoured", but it works with Android, BlackBerry, Mac, Windows and Linux and it's a two-way connection.
The SDK also has an emulator so you can develop your program and test it out before you actually have to buy the hardware to run it. Code is written in C and there isn't much space to cram everything into - 32KB of flash and 8KB of RAM. As well as Bluetooth it has a buzzer, a single input button and an OLED 96x128 screen. The processor is a 52MHz ARM7 but this mostly doesn't matter because you code in C. The battery life is claimed at 4 days and charging is via a micro USB connector.
So what could you use it for?
Before you ask, yes Doom has already been ported (partly) and it runs in a semi-convincing way - one control button is something of a limitation!
Doom on a watch
You can code a server on your PC in any language you like and send messages to the watch via Bluetooth, so this means you can use the screen to display more or less any status information you like. If you want to use it with a mobile device then you obviously need to create an app on that device that can talk to the watch.
There are already some standard apps for the watch, iTunes, various watch faces, ping stat, PowerPoint controller, notification and alerts. There is forum where you can chat and share apps but at the moment there is no official app store.
This is clearly another hardware device in search of a killer app - but what does it matter, it sounds fun and if I can already think of serious uses for it then it can't be that hard.