Installing a security system has long been considered the domain of professionals - uniformed men and women who build an electronic shield around your home and monitor it from a command center.

At least that is what the commercials always seem to suggest.

But a new breed of home-security systems promises to be simple enough to install without professional help, cutting the cost of traditional alarm systems by taking advantage of technologies such as wireless connectivity and battery-operated sensors.

Some of these systems even allow you to monitor your home yourself, using a Web browser on a computer or a smart phone. Following is a roundup of new ways to keep your castle well guarded.

The first line of defense

Companies such as ADT and Brinks offer a full alarm installation at a subsidized price, but they more than make up for the discount with their monthly monitoring fees. These systems usually involve whole-home wiring and, although they offer perks like video surveillance and 24/7 monitoring, most of these features can be easily replicated with do-it-yourself kits.

The best thing about the new DIY services is that they are wireless.

There are simple security tools you can add to almost any home without much fuss, and some cost as little as $10. General Electric sells inexpensive products under the GE Smart Home name, including an Automatic Security Light Kit ($25) and an easy-to-install Window or Door Alarm ($12) that attaches to your door and doorjamb, and squeals loudly when the door is opened. This is best for rarely used storerooms or closets, as well as gates and windows you would prefer to keep closed for safety's or security's sake.

GE also sells a $10 doorstop alarm that activates when someone tries to open a door. Because it is positioned on the floor like a doorstop and requires no installation, travelers can use it to alarm hotel-room doors.