You’ve probably seen Casio watches that can do this or that gee-whiz function. Very impressive, until you find out how those functions sap the battery life.

That’s about to change with the advent of Bluetooth Low Energy. The latest Bluetooth 3.0 spec introduces simple Bluetooth functions that require only tiny amounts of battery power. This will open up whole new categories of Bluetooth devices that could run for years on a single battery.

Casio hasn’t wasted any time in adopting the new Bluetooth standard. In fact, the Bluetooth profiles that Casio intends to use are just being ratified for some of these functions.

At the Consumer Electronics Show, Casio previewed a prototype watch, labeled accordingly as the Prototype Bluetooth Low Energy Watch.

So what will this future watch be able to do? It will primarily communicate with your Bluetooth-enabled mobile phone. The watch could let you know when you have an incoming call or e-mail message. It could provide a more accurate time by resetting itself to the time provided by the phone’s cellular network. It could pass along your phone’s alarms or vibration functions, such as a reminder for an important meeting. And you could set the watch to beep if you move more than a certain distance away from your phone. That could be handy if you tend to leave your phone behind when you’re in a hurry.

Casio could build these types of functions into a watch today, but they would severely impact the watch’s battery life. Using the new Bluetooth Low Energy profiles, Casio estimates that the watch battery will last approximately two years, even if you use the wireless communication features for 12 hours each day.

Look for this watch as early as the fourth quarter of this year. The Casio rep I spoke with said it could possibly slip into the first quarter of 2012.