Autonet Mobile, the maker of an in-vehicle Wi-Fi hub that connects laptops and phones to the Internet while on the move, was counting on its partners — Chrysler, Jeep, Dodge, Cadillac and Volkswagen — to push sales of their product in new cars.

But what do you do when new-car sales dry up? As they used to say on commercials for cheesy discounters, you cut out the middleman.

Autonet quietly began to offer its hub — which has the same name as the company, Autonet Mobile — in Advance Auto Parts stores less than a month ago, and on Amazon.com last week. “Because people are holding onto their cars longer, they are looking for upgrades,” said Sterling Pratz, a co-founder of Autonet. “I believe that is a large opportunity for us.” Some boutique installers who sold them in their shops did offer them online before. This week other online retailers, like Crutchfield, will begin to sell the system.

The hubs are being used in several ways, Mr. Pratz said. About 38 percent of the buyers are businessmen and professionals who need an Internet connection at all times for work. About 33 percent are using the systems for backseat entertainment. Roughly 18 percent are technophiles using the system in the front seat to stream Internet radio and use location-based services like Fandango, which locates movie theaters and show times and sells tickets. And the remaining 11 percent of the buyers are fleet owners, including a small number of police and ambulance companies.

The advantages to the Autonet hub as compared to using a mobile Internet card for a computer are chiefly twofold. First, the cards (and phones) are slow to locate and switch between towers, which is why there are sometimes dropped calls. Mr. Pratz said that his company had made software improvements that make the hand-offs smoother and more certain.

The second difference is durability. The shock, vibration and heat in a car “is very hard on electronics,” Mr. Pratz said, but his product is made to withstand that environment.

In the first three weeks of sales in Advance Auto Parts, more than 100 hubs had sold, and about 20 sold on the first day on Amazon, both without any promotion, Mr. Pratz said.

The hardware retails for $400, but a subscription is also required for the signal. Subscriptions are $30 or $60 a month depending on how much downloading the user wants to do.

The units do have some prominent placements. They are used on “Storm Chasers,” the Discovery Channel show on tornado chasers in Oklahoma. They are also in several cars from Jay Leno’s vast collection, and in the R.V.’s of the racers Roger Penske and Kasey Kahne.