FreedomPop, a Los Angeles company that was started in 2012, works with companies that already provide Wi-Fi “hot spots” across the country, like the connections available inside McDonald’s or Starbucks coffee shops, to create a huge Internet-driven phone network.

FreedomPop, which has 80 employees, offers software that enables smartphones to automatically join Wi-Fi networks, similar to the way a cellphone automatically finds and connects to a cell tower. For $5 a month, users can gain access to a network of 10 million Wi-Fi hot spots a month, many of which are normally not open to the public, the company said. FreedomPop’s other low-cost plans use a combination of Wi-Fi hot spots and Sprint’s network. Some basic plans are free.

Republic Wireless, based in Raleigh, N.C., uses a similar approach. For $5 a month, customers can make calls or connect to the Internet solely over Wi-Fi. For $10 a month, they can use both Wi-Fi and a cellular connection from Sprint in Republic’s most popular option. Republic Wireless’s parent company, Bandwidth.com, a telecommunications provider with about 400 employees, developed a technique to move calls seamlessly between different Wi-Fi networks and cell towers.

Both companies say they are growing rapidly. FreedomPop says it is doubling its customer base roughly every four to six months; Republic Wireless says its customer base is growing 13 percent a month.

“You can’t pretend these companies are major players by any stretch. But I think their real importance is proof of concept,” said Craig Moffett, a telecom analyst for MoffettNathanson. “They demonstrate just how disruptive a Wi-Fi-first operator can be, and just how much cost they can take out.”

Google may be experimenting with a hybrid approach similar to the small companies’. A person briefed on Google’s plans, who spoke on the condition of anonymity because the conversations were private, said the company wanted to make use of the fiber network it had installed in various cities to create an enormous network of Wi-Fi connections that phones could use to place calls and use apps over the Internet. In areas out of reach, Google’s network would switch over to cell towers leased by T-Mobile USA and Sprint, this person said.