better dialling

This will not be easy: Your dialler would need to know, in which city you are (i.e. access to GPS and maps) and what local code to apply. A lot of data to be transferred over the air, probably a delay until all required data are fetched from the maps server, and a server more that knows where you are. Particularly for the last problem: I would not use such feature. (I do not think that it is sensible, to implement such feature as on-board feature: Who will ensure that your on-board geo data base is up to date?)

You wouldn't still save a number without an area code, though. Moreover, you're not tied to a particular exchange under a particular area code. What if you had moved to a different area code between typing and dialing? Easy in a moving vehicle, or just switching cells, or with dodgy GPS reception.

More sensible would be the following idea: In your Settings you can specify a local code that is applied automatically to any number typed without leading 0 (or +). So you could specify the local code of the area you phone most often and then you can phone these numbers always without typing the local code in front -- independent of were you are (if you include the country code in the Settings, you can even dial the phone number without local/country code from abroad). However, this also has its draw back: Emergency numbers and certain provider service numbers are also without a leading 0. The work-around would be that numbers dialled from the phone book are excluded from adding the local code. But then, this is inconsistent: At one point you can dial without local code, at the other one not ... users will get confused by this.

To make it short: No. Do not do it.

I'm sure this would make a good app for those who really need it. As a built-in phone feature it would be too error-prone, though.