I introduce you: Feed+ An RSS feed generator of your Google+ posts.
At the moment Google+ API allows to fetch only public posts. Good news is that you can fetch anyone posts, not only yours.
Also, Feed+ allows to filter posts by hashtags.
For example, to generate an RSS feed of my entries about KDE I could run:
$ ruby feedplus.rb --id 104652450278570828775 -f kde > kde.xml