Tragofone - White-label VoIP Softphone with WebRTC and Auto-provisioning
Zeplin - Collaboration app for UI designers & frontend developers
PhonerLite - PhonerLite enables your PC to use it for internet telephony (VoIP , Voice over IP, SIP).
Figma Product Planner - Easiest way to plan, visualize, & share your product planing
tSIP - tomeko.net/software: SIP client for Windows.
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.