"With less than 150KB for complete SIP features, PJSIP is ideal not only for embedded development where space is costly but also for general applications where smaller size means shorter download time for users."
PJSIP open source SIP stack:
http://www.pjsip.org/
Building PJSIP for other platforms:
http://trac.pjsip.org/repos/wiki/Get...ther-Platforms
Discussion of porting PJSIP to arm linux:
http://comments.gmane.org/gmane.comp.voip.pjsip/12274