""What I personally like is the ability to know exactly where smoke would be coming from. If I were to be on the fourth floor in the middle of the night, it would say 'there is smoke in the living room'," wrote one reviewer. 99 View at eBayCheck WalmartCheck Amazon?The Roost battery is the best — well, only — option for those who already have smoke detectors, and want to make them “smart. ” That’s because the Roost battery, which is Wi Fi enabled, sends an alert to your smartphone when the siren goes off. The second generation battery looks and acts like the original, but has a much easier setup process. Through the app, which can accommodate a large number of connected batteries, you have the option to silence the alarm for up to 2 minutes, and automatically send an alert to someone else.