SIP Asterisk Multi Registrations.... SER?

I want to keep record of user’s two most recent registration locations, so that I can dial them both and whichever answers first will be connected. for example if a user abc registers from 111.222.333.444:5060 and also he then registers from 123.456.789.123:5678 , then asterisk replaces old with new registration ip. but i want that i should be able to keep both last locations and dial them.

I came to know that Sip express router can solve the problem of remembering and using many registrations of same user from different IP or Ports. is it true? how can i use this functionality?

currently I am modifying asterisk source for this. is there any other solution?

Nasir Javaid