How to implement continuity (windows + android)?

Question

Android

Apple has a continuity function that allows you to link iOS and OS X (like now macOS). In the absence of apple technology, I would like to implement such a function in a bundle of android + windows, maybe even other platforms. Can even place on Google play and Windows Store. How to implement it on a computer, I even more or less understand, but here's how to do it in order to transfer the call to the computer, I don't even have any ideas.