Long time ago i had transformed some favorite web site like Facebook,Twitter etc to desktop app without using web browser to open them in my PC,just like launching the software by double click desktop icon.If you want to turn Google+ to your desktop app,you can use Bubbles to get it done.
You can refer this tutorial
that i wrote year ago using Bubbles
how to create a Google+ desktop app
by enter https://plus.google.com
This is what a Google+ desktop app look like.