Smarthome's new INSTEON Smoke Bridge is an interesting new addition for home automation. It works with the INSTEON Hub and First Alert ONELINK smoke and carbon monoxide detectors. When the detector sounds the bridge signals the hub, which can then notify your iPhone or take other automated actions. It's not shipping yet, but it's definitely something to keep an eye on.
See also: INSTEON Hub: Automation for the Rest of Us?