Csipsimple is an open source Android project which will allow native sip for android device. It relies on the pjsip sip stack and use the pjsip-jni project. The use of this native library will ensure a better speed, call quality and less battery consumption than equivalent pure java projects. Another point is that this project will be compatible with most of SIP registrar and take advantage of the active development of the pjsip C stack.
Pjsip is an Open source SIP stack and media stack for presence, im/instant messaging, and multimedia communication
Csipsimple can be downloaded here.
Register your device with IP Comms DID Service.