The same company that provides your home phone, Internet and television services now wants to offer some protection.

A growing number of telecom providers recently added home security to their lineup of services. Their interactive systems use sensors and cameras to monitor the property, while apps let users check in remotely and receive alerts about trouble. Comcast has expanded its Xfinity Home system to 65% of its markets since the 2010 pilot. In October, Verizon introduced Home Monitoring and Control in 12 states and Washington, D.C. Time Warner Cable launched IntelligentHome in markets including Los Angeles, Hawaii and upstate New York last summer. Cox Communications and AT&T are separately in the process of rolling out similar programs.

For the companies, the services are a way to "improve their revenue per user" by tapping into the $8 billion home security market, says Tom Kerber, research director for home controls and energy at Parks Associates, a research firm. Telecoms are worried about slowing broadband growth -- 62% of households already have it, according to PewResearch -- as well as the rise in landline cord-cutting, he says. CTIA The Wireless Association reports that roughly a third of households are wireless only, up from 11% in 2006. It helps that smart-home technology has also become cheaper and more widespread in recent years, as consumers get used to using their smartphones to control the thermostat or sync with the car's entertainment system.

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These companies say their smart-security set-ups let consumers have more interaction with their home than simply arming an alarm when they leave home and disarming it when they get back. Window and door sensors and cameras interact with apps and a control panel, letting customers set rules about when the system reacts, and how. For example, "when doors open, the system takes a video of whatever made that door open, and I get an alert on my phone," says Mitch Bowling, a senior vice president for Comcast Cable. Users can also set alerts for things that don't happen, such as if the front door doesn't open by 3:30 p.m. when the kids should be home from school. As an added benefit, most systems can tie in technology to control home appliances such as the thermostat, lights and door locks from afar. So you could set the system to turn on the light when that front door opens, or turn on the a/c when you're on your way home from work, says Ann Shaub, director of product management for Verizon.

The services are typically cheaper than going through a dedicated security firm -- $10 to $40 per month instead of $30 to $75. But experts warn consumers are likely getting less protection. More elaborate home security systems can monitor for threats as diverse as carbon monoxide and rising water levels that smart systems can't detect.

In addition, some telecoms' monitoring services only alerts solely to you, without relaying an alarm in a central monitoring station that would call the police or fire department, says James Orvis, a past executive vice president of the Electronic Security Association and owner of Security Solutions in Norwalk, Conn. Miss the text that the door sensor tripped, and the police may not arrive in time to catch the burglar. It's also added risk if you're at home during a fire, break-in or other emergency where calling for help yourself isn't easy or safe, he says.

On the other hand, alerts that go only to you limits the number of false alarms, which some police departments add a fine for responding to, Orvis says. Verizon's Shaub says Home Monitoring and Control, which doesn't use a central monitoring station, still provides peace of mind and keeps consumers in tune with what's going on in the house. At the very least, it's a way homeowners can keep tabs on their kids and pets.

Shoppers should also be careful to dig into package details to determine the full cost before signing up, says Chris McGoey, a Los Angeles-based security consultant. Telecom companies' $70 to $500 one-time equipment charge is typically for a basic kit with a monitoring station and a few sensors; consumers with a large house will need to buy extra equipment for thorough coverage. So will those who want remote control over more home devices. Services may also charge extra for connectivity to a cellular network so alarms will sound even if the power goes out. "By the time you get the system that you really want, it costs you a heck of a lot more than the promotional offer," he says. Consumers may have little recourse to change their mind, either: some offers require a two-year service contract.