At present, there is only one smart battery on the market: the Roost Smart Battery. It’s not a perfect solution, but at just $35, it’s much more affordable than a standalone smart smoke detector. If your budget is limited, it’s definitely worth a look. A similar idea comes in the form of the smart listener. Again, the idea here is that you don’t rip out your existing smoke detectors, you just install an extra piece of hardware that can listen for an alarm going off and alert your phone if it hears one, turning a traditional alarm system into a smart one. This is different from the Roost battery because the alerter simply plugs into a power outlet there’s no battery backup, however, so if the power goes out, the device won’t be able to hear the siren.