Comcast joins fray of online-only live TV services with Stream for iPhone, iPad & Web

The service will be limited to Xfinity Internet customers, but allow viewing of "about a dozen" live channels, plus thousands of on-demand movies and TV shows, Comcast said. Notably live content will include HBO, and hence shows like Game of Thrones and True Detective. Subscribers will be able to watch on phones, tablets, and PCs, including Apple devices.

The service will also support cloud DVR functions, and TV Everywhere, which permits Comcast customers to authenticate with mobile apps that normally ask for a cable subscription before offering full video content.

Stream will initially debut in Boston by the end of the summer, coming to Chicago and Seattle shortly thereafter. A nationwide launch is due in early 2016.

Comcast is entering a rapidly growing market of streaming TV services that offer live TV without requiring a cable or satellite package. Dish, HBO, Sony, and Showtime have already launched products, and Apple could join in later this year. As recently as June, though, a report said that Apple was still a long way from completing talks with content providers.

The announcement comes on the heels of a letter sent to Federal Communications Commission chairman Tom Wheeler, signed by four U.S. Senators: Democrats Bernie Sanders, Elizabeth Warren, Al Franken, and Edward Markey. The politicians complained that only 37 percent of Americans have more than one option for broadband Internet, and asked the FCC to investigate how cable and broadand companies charge their customers.

The letter was particularly concerned with Time Warner Cable, which has been accused of rapidly jacking up rates such as modem fees. A pricing probe is more urgent in light of Charter's proposed buyout of the company, the senators said.

Comcast also has a monopoly in many U.S. markets, though having to compete with companies like Apple and Dish could reduce its dominance in the TV sphere.