It's an open source app for Windows Phone 7.5/Windows Phone 8 which uses APIs from Google+ Desktop Web version to make you be able to log in, post/view/+1/reshare/comment posts. view your in your circles, view your or others profile. More function are still adding.
Who made it?
It's made by Simon Chan (https://plus.google.com/104683496280574876065
), you might interest in it's development, just contact me on Google+, thanks!