The best place to start if you need help with a specific product is to contact the developer. All WHMCS Marketplace developers have both a website and support URL listed.
Covering latest version
Switch language, currency and your client area template basing on a customer's location.
Automatically detects visitor's location by IP and sets the language and/or currency you defined for that particular country.
Here you get a German translation of all WHMCS E-Mail Templates
Fully supported Automatic Currency Selection WHMCS! The customers currency is detected automatically during their first order and set, so they always get to pay in their own currency!
German translation of the WHMCS language file for the Admin area