occamsrazor
macrumors 6502
Unless I'm misunderstanding the request, you can already do this. I keep many accounts registered simultaneously. Gizmo5, sipgate, voipcheap, etc. I even have two separate GoogleVoice entries, one that dials out using my Gizmo5 account, one that dials out using my sipgate account. Acrobits Softphone has supported multiple registrations for quite a while.
All true. An alternative way to do similar is to use www.pbxes.com as a virtual PBX and have all your SIP accounts including Gizmo5 registered to that. Then you can just register Acrobits/Groundwire to pbxes. I think there are some advantages in both ways.