I'm pretty sure it is a home-grown job.
Definitely not WordPress or Joomla, but to me that shouldn't matter.
Back in the day, you could copy & paste some code that pointed to an Applet or whatever, and the next thing you knew, you had some new functionality, like:
- National Debt Counter
- Visitor Counter
- Time & Temperature
and so on...
To get what I described in my OP, you would really just have to capture each visitor's IP address and then pass that on to some Add-On/Applet/Weblink which would do the conversion and figure out what City/State/Country each visitor was coming from.
I'd show you an example of what I mean, but the whole point is that this service this person used just went out of business and so the freebie is no longer available.
But I just assumed these were very common?! :-/