Zoiper, the free softphone to make VoIP calls through your PBX or favorite SIP provider. Available for iPhone, Android, WP8, windows mac and linux
VoIP SDK, SIP SDK, Softphone SDK for Android, iOS, Windows, Mac OS, Linux, PortGo Softphone. VoIP Anti blocking, IP PBX, PERS, SIP PBX, IMS SDK and IVR SDK.