The units are for the most VOS (Voice Activated) and have a quality and sensitivity control (accessible via PC ONLY!) These audio recording devices do not require and App because they do not connect to the internet, usually they are standalone devices that will need to be placed in location and be retrieved to listen to the recordings, to playback any audio you must use a windows PC or you can connect via your smart phone with the accessory called the OTG adaptor (sold separate) and accessed via the phones "Files" folder on Apple or "My Files" on an Android phone.
