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I have a smoke detector on the ceiling outside my kitchen. Well, I had a smoke detector outside my kitchen. The alarm would go off when I was cooking a steak or something equally smoky. And, it would chirp annoyingly when the battery would run low. So I removed it, which is a dangerous thing to do, even though I have two other smoke detectors in my apartment.

The Roost Smart Battery is an elegant and inexpensive solution to both of my problems: This $34.99 device is essentially a 9-volt battery with Wi-Fi and some smarts built in; it not only will power your smoke detector for 5 years, but will send you an alert to your smartphone when it goes off. While the Roost Smart Battery isn't as full-featured as the Nest Protect smart smoke detector, it's a low-cost way to get more control over your smoke detectors without having to install anything other than a battery.

Installation and Setup

After installing the Roost Smart Battery App on your phone (iOS 7.0 and Android 4.2 and higher), you have to set up a free account by adding your phone number. The app then sends you an access code via SMS to complete the registration.

Next, the app asks you the location of the smoke detector that you will use with the Roost battery — the hallway, upstairs hallway, master bedroom, bedroom, kitchen or a custom location.

After you enter the password for your Wi-Fi network, the app then has you place the battery and your phone next to each other on a table, and instructs you to turn up the volume on your phone. (Note that the Roost only works with 2.4-GHz 802.11b/g/n networks.)

Your phone then plays a loud obnoxious noise for a few seconds — it sounds like an old-school dial-up modem — to transmit information to the battery. Once the battery connects to your Wi-Fi, the app then instructs you to install it in your smoke detector.

In all, the entire process took about 5 minutes. I had to go through the pairing process twice, but it wasn't a big issue.

Interface

The Roost app is pretty basic: The home screen shows which batteries have been installed and their current status (such as "OK"). Selecting a battery brings up a screen showing its current battery life, the last activity of the smoke detector, its location and a Snooze button.

A settings menu lets you change your profile and add emergency numbers (like 911) as well as additional monitors. When you add a monitor — someone who will also be contacted if the alarm goes off — you can specify from which smoke detectors they'll receive an alert. However, that monitor will also have to install the Roost app and create an account, too.

Performance

The Roost worked as advertised. I used a can of fake smoke to set off my smoke detector, and after about 2 seconds of it blaring, I received an alert on my iPhone, and the Roost Battery's icon in the app turned red. I was given the option to call an emergency contact, view the other monitors or snooze the alarm.

If you have interconnected alarms, when one of them sounds, the Roost will alert you, even if its battery isn't installed in the alarm that went off.

The Snooze button will disable the smoke detector for about 2 minutes, but this feature will work only on alarms that rely solely on the battery for power. This, too, worked instantly, and will be a real boon to cooks who like to flambée. You can't "un-snooze" the battery manually; it will switch back on after a few minutes. Still, this is probably one of the best features of the Roost.

Battery Life

Roost says its lithium battery should last for more than 5 years. For the purposes of getting this review up in a timely manner, I couldn't wait that long to find out. When the battery does run low, it will alert you in the app before the alarm starts chirping.

Once the battery dies, you can remove the Wi-Fi module and purchase a replacement battery for $14.99.

Roost vs. Nest Protect

Unlike the Nest Protect, the Google-owned smart thermostat, the Roost is much more limited in features, which is to be expected given its price. A single Roost battery costs $34.99, while a two-pack costs $64.99.

By comparison, a single Nest Protect costs $99, but is a more powerful product. For example, the Roost doesn't connect with any other smart home systems, while the Nest works with a wide range of products. (Roost should work with IF-This-Then That later this year, according to the company’s website.) Additionally, the Nest Protect monitors both smoke and CO2, and gives spoken alerts, such as "There’s smoke in the kitchen."

Bottom Line

The next time the battery dies in one of your smoke detectors, you should seriously consider picking up the Roost Smart Battery, if only for the fact that it should last up to 5 years. However, the Wi-Fi smarts in the Roost make it an easy way to turn any smoke detector into a smart home device, and alert you from afar when it goes off. The Nest Protect does more, but if you don’t want to replace the alarms you already have, go with the Roost. And, yes, I now have a working smoke detector outside my kitchen.