Within five years, industry watchers say, remote monitoring systems will be standard add-ons to your cable or phone service. But if you're not inclined to wait, there are a handful of out-of-the-box versions on the market now that are easy for homeowners, even nontech-geeks, to set up and use.

The simplest type of system works on radio-frequency technology. A base station about the size of a hardback book keeps track of battery-powered sensors you install around the house. You can get sensors that detect whether a door or window is open or closed, if a toilet is leaking, or if the temperature drops below a preset level. If you're worried about pipes freezing in the basement, for example, stick a sensor to the spot at greatest risk (most come with double-sided tape), and you'll get an alert when the mercury falls. Flood sensors send a message when they're covered with water. Place them under the water heater or behind the washing machine; I could have used one under my bathroom vanity.

In addition to these basic sensors, most systems offer a range of add-ons. Put a motion detector in the hallway, and you'll be alerted if a toddler or an elderly relative gets up in the middle of the night. Stick a tilt sensor on your garage door—or the lid of your jewelry box—to know if it's been opened. One system, Eaton Home Heartbeat, has a power sensor, which can tell you if you've forgotten to turn off the coffeemaker or iron, or if the kids are watching TV when they're supposed to be asleep. Power sensors can also notify you indirectly of an emergency, say, if your sump pump or well pump unexpectedly turns on. Eaton also offers a water shutoff controller: Install the motor-driven valve on the supply pipe, then position wireless water sensors anywhere you fear a leak. Within seconds of water detection, the sensor sends a signal to the controller, shutting off your main line.

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