Still, if automakers were to begin developing apps for CarPlay, it could open a new avenue for hackers, experts say. And there are already potential vulnerabilities, as the government’s Defense Advanced Research Projects Agency has demonstrated in experiments showing how a criminal could remotely take control of a connected car.

“There are absolutely security issues,” said Robert Clyde, international vice president at Isaca, a nonprofit organization focused on information technology security. “Could a bug in iOS or in Android give someone access to critical systems?” Apple and Google declined to comment.

Once a problem is discovered, there is also the practical problem of updating the software, which in many cases would require extensive testing to ensure that no new conflicts were introduced. In most cases, drivers would then have to return to the dealership for a software update.

Most automakers have already invested considerable time and effort in developing their own connected car systems. Ford has had such a system for more than seven years and is introducing its latest version, Sync 3, this summer. Sync 3 already supports a multitude of smartphone apps, taking the more traditional approach of having companies like Pandora develop apps for its system, rather than the other way around. To make the process easier for developers, Ford is promoting SmartDeviceLink, which would give app creators a way to write a program once that could then run in any compatible car. Toyota has said it is studying SmartDeviceLink as well.

There is also technology’s rapidly evolving nature to consider, Mr. Hanna said. “The apps are going to come and go,” he said, pointing out that Ford’s Applink software now supports Apple and Android — but not BlackBerry.

The lesson: Automakers cannot afford to hitch their connected car future to any one device.

Moreover, many drivers will not want to be forced to rely on a smartphone in their vehicles, so car companies will have to continue to develop built-in connected systems — especially with self-driving cars on the horizon, some experts said.

“It will be impossible to do everything from a phone,” said Andrew Poliak, the global director of automotive business development at QNX Software Systems. QNX is responsible for the software behind many connected car systems, including Audi’s and Ford’s. (QNX is owned by BlackBerry.) Cars will still need built-in navigation for semiautonomous driving assistance features to work, Mr. Poliak says, as well as to meet safety and security standards.