Tax before login based on IP Geolocation

[MLu]

Can anyone point me to an answer on to make it possible to base the tax rate used on products on the customers physical location? It is not good enough if based on browser language, as for example a German speaking customer could be based in Switzerland (no tax as it is outside EU), in Germany (where we have to apply a German VAT-rate) or elsewhere in EU where he/she should pay our standard tax-rate (not over the internet treshold here). I fear that I loose sales as customers are confused/angry when prices suddenly change after they have logged into/created their account.

 

I have noticed that for example the "Who's online" add-on has some functionality included that seemingly is based on a (free) geolocation service.