I have several SIP devices (software, hardware, mobile) which mostly need to call each other, and only occasionally talk to external "real" (PSTN) phone numbers. These devices don't require having each a real unique PSTN phone number, which is a "valuable resource" (AAISP charges a monthly rent for each PSTN number). An AAISP VoIP user could have a single one primary VoIP account with one PSTN (geo) phone number, and many other internal accounts linked to the primary account. Devices registered (SIP) with internal IDs can call each other freely, and use the primary account to call outside AAISP. For incoming calls, the primary account can forward to internal IDs according to rules. VoipTalk.org and other providers offer just that. Indeed, I'm currently using the free internal SIP accounts from VoipTalk.org for internal calls, and one AAISP account for external calls. It would be nice to consolidate it all with AAISP, without unnecessary additional PSTN numbers.