Hi I've tried writing a connection piece between websocket and unity SDK some time ago, but back then (don't know if things changed significantly with v4) it was a hot mess. Most classes were far more complex than their interfaces let on and had dependencies running through most of the sdk. So in the end I figured I would have needed to replace far more than the service provider (and even that seemed far from straightforward) to make this work. Also the websocket data doesn't match the data used by the unity sdk. Don't ask me why. You will have to parse the websocket data and and reverse engineer/guess/imagine it into the data used by the unity sdk.
Didn't look that much at the circumventing the websocket stuff with some LeapC API to network stuff so can't help you there unfortunately.
You can use the Hololens in conjunction with the Leap Motion when using the Holographic Remoting Player, as everything is then basically running in the editor on your pc, making accessing the Leap Motion quite easy. However this method is extremely sensitive to the quality of your wireless. Using Remoting Play even with mediocre wifi is really no fun.
If someone else has a good solution for connecting these two devices while benefitting from the sdk I'd also be happy to hear that.