RingCentral Embeddable is an all-in-one widget that can be installed in any web app with just a few lines of code.
Rainbow Office Embeddable Voice and Text Widget
Rainbow Office Embeddable enables developers to quickly embed voice and text into their web applications. With Rainbow Office Embeddable, you can embed a full-featured softphone into your favorite web application for an integrated communications experience that drives productivity and ease of use without lengthy development time.
Please reference https://developer.ringcentral.com/embeddable-voice.html for install details.