Sure, I've done it in my 60-year old home. I prefer hard wiring because it's concealed and the sensors are much cheaper. If you have an accessible basement or attic the wires can typically be fished through without too much trouble.

As for the EMF, that's another issue, and in my opinion, as someone whose career was environmental engineering and risk reduction, your worries are misplaced. Wireless sensors will contribute negligibly to the background EMF you already have. If you are really concerned about the supposed health risks from EMF -- and that's another topic I won't choose to debate here -- you should get rid of electrical devices in your home as they generate EMF: televisions, telephones, battery chargers, lights and lamps, fans and air conditioners, power tools, dishwashers, toasters, clothes washers and driers, hair dryers, clocks, electric ranges and hot water heaters, computers, microwave ovens, clothes irons, baby monitors, etc.,...in fact, anything with a cord that is connected to the electrical system in the house whether the device is on or off. You should also realize that the wiring in your walls produces an EMF field all around you. It's good to be aware of environmental risks, but there are much larger and certifiably more real ones out there than exposure to EMF. So, if you can't put in an alarm system with only hard-wired sensors, don't worry that you are doing something bad to your family by using a few wireless sensors.

You might want to check the bottom of the 'home security control panel location' topic for my post on making simple, reliable door locked indicators. I've always considered that a weakness in alarm systems that all they check is if the door is closed, not locked.

The reason you want it hardwired is for reliability.

If you sent this message off your WiFi enabled tablet/laptop, the RF radiation has much exceeded anything these devices could ever put out.

The installation of low voltage wiring can be tricky, but also allows many more options than 120 volt AC wiring. Just find somebody competent to do it and don't worry about it.

Thank you for all the responses. I did go with the wireless one from ADT.

According to them, its not a wifi(always broadcasting its signal) it only really communicates when a change occurs ie... engage/disarm the alarm, or when a window or door is open.

I might get a EF meeter, not just to check the security device but other stuff in the house..just out of curiosity.

anyone know of one that is good and reasonably priced?

thanks.

You know, there is nothing wrong with being concerned about EMF that can be radiated within your home, but it needs to be put into perspective.

People will concern themselves about small radiated signals from wireless devices in their home but think nothing of carrying a cellphone in their pocket all day long.

Every time that cell phone tags up with your carrier, it is sending out considerable RF energy that far exceeds the energy of any of these other devices.

With
hardwired security system, the installer will have to drill holes in the walls.
You can use it under the carpet but, every place keeping the wires under the
carpet won’t be possible. Also excellent wired systems are having wireless
capability.

Both my houses were prewired for alarm systems. The one I installed in the townhouse is done entirely with (GE/Interlogix simon xti) wireless components. Works as well as any alarm I've dealt with. The other house has a lot of hardwired sensors but a few wireless ones as well. It's also GE (one of the older Concord systems).

Running wires under carpet is problematic (and illegal unless the cabling is specifically listed for such).

My first house was built in 1952 and I had it hardwired for a security system in the late 1970's. It was a single story ranch house on a slab but with an attic. The installer had no problems hardwiring all the doors and windows, including internal doors, without drilling into the walls or doing anything that required repairs. Some wires were fished and some wires were run behind moldings. When we later added a second story, we simply ran a piece of large diameter conduit up inside the walls while they were being built so that we had an easy way to run more wires back down to the panel. It was an invisible system that was still functioning perfectly 25 years later when I sold it.