This application turns your phone into a full remote surveillance tool! However, you are not the active spy, but the phone will alert you whenever something interesting is happening.
The basic setup is simple. Set the "agent" - that’s the contact’s telephone number that should be informed in the case of an emergency. Next, place the phone at the place that you want to monitor, for example next to a baby.
From now on, the application will constantly monitor the audio level of its surroundings. If they exceed a pre-defined threshold, the phone will automatically call the agent. As a normal voice call is made, you can now hear the surroundings of the phone in order to judge if something serious is happening.
Technical Background
The audio processing is done in two tasks - one records the current surroundings, while the other analyzes the previous recording. This would provide an ideal starting point for further sound processing. For example, it would be possible to analyze the frequencies of the sound to judge if it could really be a human voice.
The application is developed in Python for S60 and is available for free as open source. Installation instructions are included in the download.