Connected to a burglar alarm or fire alarm in the event of making phone calls playing voice messages. Controlled via DTMF actuators can operate on the spot.
In recent years we have introduced several telecontrols based on the SIM900 GSM module. We released schematics and code for a gate opener (that activates when receiveing a call from a given number), a GSM thermostat to manage the temperature of remote houses with simple text messages, a remote alarm control with DTMF and, last but not least, a remote alarm with I/O and controlled via calls or SMS.
Many of these tools send text messages or place phone calls in response to changes to the electrical inputs. In some cases, especially when the receiver is a human, nothing is like a voice that clearly yields you screaming “fire in progress!”, or”thieves in the house!” etc. [Via]