With the ink still wet on GM's purchase of Cruise Automation, a San Francisco startup working on autonomous-driving technology, early-stage investors and entrepreneurs in Silicon Valley and beyond are chasing the next big score.

The acquisition of Cruise, rumored to be worth more than $1 billion, signals that automakers, historically wary of high-priced technology deals, may now see them as necessary to avoid falling behind Google and Uber, which aspire to offer self-driving cars that can be summoned from a smartphone.

"It's unusual that you'd have that large of an acquisition of an early-stage company," Steve Goldberg, a partner at Palo Alto, Calif., venture capital firm Venrock, said at a March 23 conference in San Francisco on the business of autonomous vehicles. "I think Cruise is an indication that [automakers] think they don't have the expertise, so they're willing to acquire technology and keep it proprietary."

It remains unclear whether the $1 billion figure is accurate, or what it refers to. Neither GM nor Cruise has publicly commented on the scale of the deal. Acquisitions this large also routinely come with caveats -- for instance, a requirement that the team being acquired achieve certain goals to receive the maximum payment, said Alexei Andreev, managing director of Palo Alto, Calif.-based AutoTech Ventures.

"Clearly, the early investors made something like a 100-times return, and a 100-times return is something that turns heads," Andreev said. If the $1 billion figure is accurate, he added, "we will see more activity and increasing valuations. Undoubtedly so."

Three-year-old Cruise, best known for working on an aftermarket kit that would enable a highway autopilot system in late-model Audi A4 sedans, is one of several start-ups across Silicon Valley working on software for self-driving cars.

Menlo Park, Calif.-based Zoox received permission in March from California regulators to test self-driving cars on public roads. Drive.ai, a startup from nearby Santa Clara that was spun out of Stanford University's Artificial Intelligence Lab, bills itself as developing software for self-driving cars.

Then there's Hotz, the brashest of the bunch, who captivated an audience at the South by Southwest arts festival and tech conference with his stories about how he was courted by Tesla and how he built a self-driving Acura in his San Francisco garage.

Hotz, known online as GeoHot, became famous in hacker circles in 2007 as the first person to crack the security Apple Inc. had devised for the iPhone. He was 17.