An electronic device may include a smoke detector. The electronic device may use the smoke detector to monitor for the presence of smoke. In response to detecting smoke with the smoke detector, the electronic device may issue an alert or take other suitable action. The electronic device may transmit alerts to nearby electronic devices and to remote electronic devices such as electronic devices at emergency services facilities. Alerts may contain maps and graphical representations of buildings in which smoke has been detected. Motion detectors and other sensors and circuitry may be used in determining whether electronic devices are being used by users and may be used in determining where the electronic devices are located. Alerts may contain information on the location of detected smoke and building occupants.