Fonid is an app for portable devices or wearables (smartphones, smartwatches, etc.) that uses their capabilities to continuously capture audio and generate visual / vibrating notifications when certain sound events are identified. The key to provide always-on operation without compromising all-day battery life is a combination of proprietary audio processing and machine learning algorithms that achieve high accuracy identification with very low computational cost. Such all-day always-on operation would not be feasible by performing the sound identification on a Cloud server due to the power consumption of the audio data transmission itself (comparable to that of an all-day long phone call). In addition, performing the sound identification locally on the device avoids the privacy issues associated with sending continuously recorded audio to the Cloud.