[phyrrus9]

It worked based on geo-IP (which is not terribly accurate but that was the point after all), and I'm not sure if members are too keen on sharing that information with me

Make a simple PHP script that prompts them to share location data, geocode it, and then call it good. An IP address doesn't mean anything, if a member is too scared to share it, they probably don't know a whole lot about tech.

Surely, if they're too scared to share it, they wouldn't want anyone to meet them in person?

Or, for added security, users can just opt in on the usercp, and we can write up a script that geocodes based on site wide tracking.