[exim] Tricky DNS servers [OT]

I have a few weird ideas and would need a smart DNS server of some sort
to pull it off. Basically looking for a programmable backend that might
do DNS lookups itself.

Here's a possible example. There are servers out there that return
country codes of IP addresses. But what about a country code for a host
name? You would have to do an IP lookup on the host and then use the IP
to get a country code.

So - is there source code for something like this or a DNS server with a
scripting language?