Additionally, the Nest Protect is compatible with other smart home networks including Nexia, Vera, Wink and Google Home; it doesn't work with Amazon Alexa or Apple HomeKit. Unfortunately, the two year warranty is shorter than those from First Alert and Kidde. Read the full reviewBest ValueKidde KN COSM B RF$49. 72 View at AmazonCheck Walmart?Detects both smoke and carbon monoxideDoesn’t require a hardwired connectionCan connect to multiple alarms via Wi FiPerformed poorly in our detection testsRequires extra equipment for the mobile appOnly compatible with Wink smart home platformThis alarm is two devices in one: a smoke detector and a carbon monoxide detector. It’s very easy to install because it runs on changeable batteries so you don’t have to hardwire it into your home’s electrical grid. If the Kidde KN COSM B RF detects an emergency in your home, it sets off a tone alarm as well as a voice alarm that gives instructions and tells you what the danger is.