Hello, Henning!
you probably already investigated this, but are you aware of the http_query function in the utils module?
http://www.kamailio.org/docs/modules/1.5.x/utils.html#id2454145
If this don't meet your requirements yet, perhaps it can be extended?
Yes I know about http_query(). But I would like to call save() or locate() or alias_db_lookup() instead of scripting.