Before you blink the feature is there - add geo location information to your Ajax applications.
If you want to know where an IP address belongs to, you now can use a free service. As Volker lets us know, you could have the whole database at your (local) service. But why do all the heavy lifting if you just need an IP address from time to time? iplocationtools offers a simple REST API to query an IP address returning a XML or CVS result. The only thing missing was a JSON return value (and JSON *is* the flavor of the day isn't it?). So I asked nicely and about 7 hours later (given the difference in time zones: that is pretty instantly after getting the first coffee into your face), the interface is ready. Now I wish other ideas would be implemented with the same speed.