Comcast is adding another service to its quiver as the cable giant aims to appeal to cord-cutters and remain competitive with emerging online services. On Sunday, Comcast announced Stream, a $15 monthly add-on for Xfinity Internet subscribers that gives them access to live and on-demand TV online. Stream offers a limited number of live TV broadcasts from "about a dozen networks" including the major broadcasters (ABC, CBS, Fox, and NBC), as well as HBO.

Stream will launch by the end of summer in Boston, followed by Chicago and Seattle. The company plans to offer Stream to all Comcast customers by early 2016.

Twelve or so live channels is decidedly less than the more than 70 live streaming broadcasts available to Comcast's television subscribers. Nevertheless, it's still a good amount of television and by offering the major broadcast networks Stream could be a better deal than upstart Sling TV.

From the sounds of it, however, Stream may be a little more restrictive than Sling. In its blog post announcing Stream, Comcast said the service will let Xfinity Internet subscribers "watch live TV... on laptops, tablets, and phones in their home."

That  "in their home" bit sounds a little concerning. Does that mean you have to register specific mobile devices to use Stream (i.e. mobile devices that are typically in your home), or does it mean live streaming TV is only available when you're in range of your home Wi-Fi? We've dropped Comcast a line and will update this article should the company respond.

Even if you can only watch live TV when you're at home, you won't be totally at a loss for content when you're out and about. Stream also gives you the rights to use Comcast's TV Everywhere service via the Xfinity TV app for on-demand viewing and access to Comcast's cloud DVR service.

The impact on you at home: In recent months, Comcast has been rolling out a variety of programs and features for the streaming revolution. In August 2014, Comcast announced Xfinity on Campus, a live and on-demand streaming service for college students. A few months later, in October, the company rolled out its stream-anywhere cloud DVR. More recently, Comcast expanded its live and on-demand streaming selection for regular TV subscribers.

Good, but not too good

Comcast's announcement was short on details such as a complete channel line-up, but in many ways Stream feels like it's striking a delicate balance. The service will likely be good enough to prove competitive to Sling in terms of content--yet it doesn't have enough channels to convince hordes of TV subscribers to give up their fat cable packages.

Instead, Stream is an appeal to Comcast's current Internet-only subscribers who might be looking to add a little TV back into their lives at a cheap price. Stream sounds like it could be a nice deal, but it's hard to say for sure until Comcast offers more information about what content you get for your dozen channels and any restrictions the company places on the service.