Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
Price2Spy - Price2Spy is a price monitoring, pricing analytics, and repricing tool, meant to help eCommerce professionals keep an eye on their competitors or retailers.
Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
Skuuudle - Discover, match and monitor your eCommerce competitors.
MicroSIP - MicroSIP is a free portable SIP softphone for Windows based on PJSIP stack.
Prisync - Prisync is a competitor price tracking and monitoring software for all sizes of e-commerce companies worldwide.