Put your old or second iPhone/iPad in the hallway and start this app. The app reacts to noises, e.g. doorbell. When it is detected, a dog barking sound is played. This is intended to deter potential burglars. Can also be linked to AirPlay devices, e.g. speakers to achieve a higher volume. The app must remain active for noises to be detected. You can dim the screen or place the iPhone face down (screen is switched off) to save energy. 8% energy is used in 12 hours. Connecting to a power source is also helpful, but not necessary.
