Subscribe to geo-content?

Hello

Sorry if this has been solved / discussed elsewhere, I can't find it. Has anyone had a go at implementing a geo-version of subscribe? E.g.:

• I want to know about any 'events' posted within an x km radius of my position?

It would be a little computationally expensive, but not orribly so I don't think. Example:

http://www.assemblysys.com/dataServices/php_pointinpolygon.php

Though it would depend on how many users there were... perhaps it could be set as a cron task. (Are subscription notifications already cron tasks?)

I can't think of any other way - other than attaching overt taxonomy-term placenames to events.

Thoughts?

Cheers,

Dan