Better wristwatch: self adjusting accuracy

Ever own a watch, particularly a digital watch, which always seemed to gain or loose about the same amount of time each month?

Each time you set the watch, why can't the watch realize it's been too slow or fast since the last time it was set and attempt to regulate itself?

To do this properly, the time piece would need to maintain a small amount of memory to keep track of the last time it was set and by how much it was off. Using this info, just like a phase locked loop (PLL) the watch could narrow itself closer and closer to an acceptable accuracy.

Unfortunatly, the precision of a watch usually varies based a tiny bit based on temperature. Different watches run at different speeds on different people. A wristwatch could have a temperature sensor in it to try and correlate automatically the changes in temperature to the changes in speed.

The wearer would have to set the watch using the same synchronized time source each time. The more often it was set, the more data points the watch can collect in order to set up the PLL. Such synchronized time is widely available: the talking clocks which you can telephone, the hourly beep you hear on some radio stations, and even software exists which uses NTP to accuratly set the clock in your computer.

Perhaps it would be useful to have a "regulate" mode and a "set" mode where the wearer would put the watch in regulate mode for the first few months or when he/she wants to reregulate the watch.

Such regulation would essentially ignore changes in minutes greater than say 7 minutes. All of the time zone changes I've encountered are on 15 minute boundries (between India and Nepal for example).

Drawbacks to this idea are that it could be quite complicated for the average consumer to use. Consumers who didn't fully understand the ramifications of setting their watch could end up with watches which ran very fast or very slow.

Another drawback is that this is not a zero cost to manufacturers. Not only is there some software to develop, but some additional memory within the watch will also be necessary. Memory in these small packages is apparently not cheap. It consumes power and space on the chip, thus adding cost.

Even if this idea is unworkable automatically, I would love to see a digitial watch which allowed me to regulate it by bumping up/down some digital register within the time set mode. This would at least allow one to manually regulate a digital watch. I've never seen such a setting on a digital watch, though I have seen the tiny set screw in the back of the case which is quite near impossible to set with any precision. I would imagine that something like this would be fairly trivial for a company like Casio to add to all their new watches.