Broadly speaking, there are two approaches to home automation. One is to have a personal computer that's dedicated to acting as a central controller. Clearly I'm a big advocate of this approach, and I practice what I preach (as the saying goes), because it allows you to build the most flexible and "smart" home automation system.
The other approach is to deploy individual semi-smart devices, each with a special purpose and single function, but none of them communicating with each other. This is a valid approach too, of course, and if you have just a few things that you want to accomplish its often the least expensive route. For some, these devices are the "gateway drug" to full home automation. That's my story, I started with this approach then quickly moved on to a centralized controller when I wanted a more integrated system.
Nevertheless, lately I've begun to re-discover the simplicity of dedicated, disconnected hardware. I've written about my standalone webcams before, and they're still among my favorites, but a couple of new toys have caught my eye lately.
First up is the TeleSpy. It's a telephone with a built-in motion detector and microphone. Turn it on before you leave the house and if it detects anyone entering your home it will silently ring your cell phone and allow you to listen in for 30 seconds. More than enough time to determine if there's something going on that you should worry about. It's a regular phone, too, so it doesn't appear suspicious and has utility beyond home security. (If you have pets, of course, you'll need to consider where you place it in your home. One of the contributors to Smart Home Hacks suggests that putting it in a room with a closed door adds an extra layer of security. This will reduce false alarms and when you get the call you know that someone has opened the door, a good indication that Fido isn't the culprit.)
I'm also intrigued by the Water Warning Leak Alarm. It's a battery-powered box that emits a shrill alarm when its sensor detects moisture. If you have a damp basement or a leaky water heater, this can bring you peace-of-mind. Edward Cheung describes how alter a smoke alarm to build a water detector in Smart Home Hacks (See page 169) but the low cost of the Water Warning makes the pre-built approach well worth considering.
The bottom line? When the cost of a standalone device is relatively low, and its utility immediately beneficial, I no longer hesitate to consider adding one to my home.