They're still limited to the San Francisco Bay, but they're now available to plumbers, locksmiths, house cleaners, and handymen. This older article from SEL covers the basics. And the big news today is that more services were added and access has opened up through AdWords Express.
Local businesses and professionals in the SF Bay area fill out a simple form with their information and submit it to Google, who screens everyone and runs background checks. If Google thinks you're "trustworthy," they give you a profile page. Then you can manage bids in AdWords Express to compete for the top spots. They appear at the tippy top of the SERPs, so they could be a useful form of advertising. Time will tell!