Mobile SIP Clients
I spent some time messing with SIP clients on my mobile to connect back to my Asterisk server, but a lot of the time it was more trouble than it was worth, particularly when dependent on a data connection. However, AAISP have just re-launched their SIP2SIM service, so with a sip2sim sim in my phone and it bit of configuration in Asterisk / 3CX, my mobile becomes just another extension of the phone system, but operating on the mobile network (O2 provide the network). No messing with SIP clients, it just works, even on a 2G connection.