Former Windows chief Steven Sinofsky is jumping into his new role at Andreessen Horowitz by joining the board of auto-sharing company Local Motion, which also secured $6 million from the VC firm.

"Local Motion is bringing to market a unique combination of hardware, software, and services that redefine the way fleets of vehicles can be deployed, used, and managed," Sinofsky wrote in a blog post.

Andreessen Horowitz will provide the company with $6 million in Series A investment, while Sinofsky will join the Local Motion board with co-founders John Stanfield and Clement Gires. The move comes about a week after Sinofsky joined Andreessen as a board partner.

Local Motion developed technology that can be added to cars to allow for app-based sharing. Fire up your smartphone, locate an available car nearby, unlock it with a key card, and you're on your way. As Local Motion describes it, the service is currently being targeted toward businesses with fleets of cars. Employees can use their ID badges to unlock cars, and cars can be booked via calendar invites for those who need to go to off-site meetings.

Despite the current focus on the enterprise, Sinofsky said "it's easy to imagine a future where their technology could be used with any car." Zipcar offers a similar service, though you have to book in advance rather than just walking up to an available car at will.

Sinofsky talked up Local Motion's simple design, which designates free vehicles via a green light in the windshield and sends text messages if you forget to plug in an electric car.

It's powered by "powerful hardware," he said, via a small box under the dash that takes about 20 minutes to install. "The hardware works in all cars and offers a range of telemetry for the fleet manager beyond just location," Sinofsky wrote. "In modern electric cars, the integration is just as easy but even deeper and more full-featured."

With more and more vehicles on the road - 800 cars per 1,000 people in the U.S. - car sharing is a great way to reduce congestion, pollution, and resource consumption, he said. But right now, managing business or government fleets "is a surprisingly manual process," so a service like Local Motion could help.

Sinofsky left Microsoft in Nov. 2012, shortly after the launch of Windows 8. In December, he announced that he would head to Harvard Business School in the spring of 2013 to teach "product development" and write articles about the topic. Sinofsky will remain at Harvard while working on Andreessen Horowitz projects.