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Smart Home

Roost's new battery brings mobile brains to old smoke detectors (hands-on)

The Roost Smart Battery packages Wi-Fi connectivity into a 9-volt package. Put it into your old smoke detector, and you'll know if it sounds no matter where you are.

Tyler Lizenby/CNET

Editors' note, November 11, 2015: The Roost Smart Battery goes on sale today, and the piece has been updated with hands-on impressions.

Stuffing Wi-Fi capability into a 9-volt battery, the Roost Smart Battery can be put into any smoke detector. When the alarm sounds, it'll send you a push notification, wherever you are. You'll also be notified when the battery starts running low, allowing you to avoid the typical chirping, though Roost doesn't expect that to happen often, claiming its battery can last up to five years.

Roost wrapped up a successful Kickstarter campaign last fall. Today, you can order the batteries on Roost's site, as well as Amazon and Home Depot. Individual units retail for $35 and a pack of two costs $65. Replacement battery packs cost $15.


During the initial crowdfunding campaign, I had plenty of concerns about the Roost Smart Battery. The tech startup behind the 9-volt battery -- simply called Roost -- looked to be squeezing a lot of functionality into a small space, and I was unsure that it could pull it off.

Well, I've now held Roost in my hand, and I can testify that it looks just like a regular 9-volt with a spiffy coat of paint, and it works. Not only that, Roost seems to work quite well. Again, I've only gotten to spend about a day with the battery, so I still have a few questions and odds and ends I want to test, but so far, so good.

Installing Roost and getting setup on the app are both easy.

Tyler Lizenby/CNET

For one, Roost nails an essential feature of any smart home device that I've seen too often neglected -- the app. Roost's software strikes a great balance between keeping things simple, but not so simple that it's plain or lacks functionality. It's compatible with iOS and Android, and walks you through setup with platform-specific pictures. My battery was connected to the CNET Smart Home router and ready for use within minutes.

Connecting the family

Via the app, you'll indicate the location of your battery, and can check on its status and battery life. You can also customize the app's emergency contact, which defaults to 911, and add "monitors," which is the app's term for additional users.

Roost's CEO and co-founder Roel Peeters emphasized to me that the smoke detector should be a "shared device" with your family, like your appliances or your TV, and not an "individual device" such as a cell phone. To that end, the app makes it easy to add additional monitors to any Roost battery, so your spouse and children can be notified of an alarm on their own phones.

A battery within

I also appreciate that you, in theory, will never have to deal with your smoke alarm chirping with Roost, and you can replace the battery when that five-year promised lifespan does run out.

The bottom of the battery pulls free when you need to replace its power source.

Tyler Lizenby/CNET

One of my biggest gripes about the initially promised product was the thought of replacing the whole thing when the battery died. Apparently, many of Roost's users had the same concern, and the company addressed it. The bottom of the unit -- the piece below the blue line -- now snaps off and can swap out for a new power source. Again, you can buy this replacement pack from Roost for $15, a nice savings over the $35 cost of a whole new battery.

Sounding the alarm

When an alarm does go off, you'll get a push notification to your phone -- your phone number doubles as the username for your account. The notification chime from Roost actually sounds like a smoke alarm. It's annoying, and I appreciated that. I want Roost to make sure I'm paying more attention to this alert than I would to a typical text message. That said, when I had my phone on vibrate, the alert buzzed typically, so you won't necessarily know something's out of the ordinary if you turn off your ringer at work.

Once you do notice the alert, pressing it pulls up the app and a pop-up window lets you select from a number of actions to take. You can call your emergency contact, view monitors, snooze the alarm, and view details.

Snoozing the alarm will be an appealing option for many after a mishap with burned toast. It's not a perfect option, unfortunately. A company representative confirmed that Roost can only silence battery-only smoke detectors, not hardwired options that use the 9-volt as a backup. That's to be somewhat expected, since Roost can't control the hardwired power to the smoke detector, but it does put Roost behind a wholesale replacement option such as the Nest Protect in terms of smarts.

The competition

The $99 or £89 Nest Protect offers similar Wi-Fi capabilities and remote monitoring, but it also detects both CO and smoke. The Roost Battery can swap into a smoke detector, or a carbon monoxide detector, but you'll need to buy individual batteries for each. Roost will certainly be a cheaper option for swapping all of the detectors in a large home with smart options, but Nest has the added advantage of interoperability in a larger smart home setup via the ever-growing Works with Nest program.

The US-only $100 Leeo Smart Alert Nightlight walks the line between the simpler option from Roost and the wholesale device replacement of Nest. A connected color-changing light, Leeo plugs into your wall outlet and listens for the frequency of any alarm, sending you push notifications and calling you should one sound.


As of yet, Roost also can't distinguish between pressing the test button on your detector and an alarm actually caused by smoke, though a Roost representative told me that's a planned feature for the future. Retrofit smarts with Roost don't have quite same effect as wholesale replacement, but so far, Roost performs well enough to be worth consideration, since it completes its main task admirably.

I'm still measuring response time, and will be testing Roost with actual smoke for the full review, but for now, I can attest that it's well designed and easy to use. I was excited for Roost, particularly the idea that smartening old electronics could be as simple as replacing the battery. Roost itself might not be perfect, but it deserves consideration, and it's showing signs of that potential coming to fruition.

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