So there seem to be 2 options:
1) Use Supercache Plugin + Use a geo plugin such as GT-Geo and try to execute that within the cached page:
Welcome Dude! You are from:
<!--dynamic-cached-content-->[geo-in country="de" note=""]GERMANY[/geo-in] [geo-in country="us" note=""]USA[/geo-in] [geo-in country="uk" note=""]UK[/geo-in]<!--/dynamic-cached-content-->
That doesnt work somehow. You can see the cached output here: http://www.top3buys.com/uncategorized/hello-world/ - it usually says Germany, since that is what I cached.
What can I do?