[OpenSER-Users] OpenSER billing options

Hi list, are there alternatives to Radius for billing integration with OpenSER? The problem Radius seems to pose me is that it is per user and therefore requires to have a full database of every softphone/SNOM/etc user, which is admin intensive. Does anyone know if there is a method of accounting data per SIP peer (for example per Asterisk system attached to OpenSER) which could record call details without needing to know about all the actual handset users? I suppose you can do anything you want with the accounting module so this is really a "does anyone already do this" question so I dont need to invent everything from scratch... thanks for any suggestions, Andy.