Microphone - Hearing Aid is a free Android app developed by PC Mehanik, falling under the category of Utilities & Tools. As the name suggests, the app is designed to serve as a hearing aid, helping users test their device's microphone and speaker, and use it as an external mic or a megaphone.

The app offers different input/output modes to use on AUX or Bluetooth external devices. However, it's important to note that not all input/output combinations are currently possible on Android. Additionally, users can tune the sound by using the equalizer and boost the volume when using it as a megaphone. Overall, Microphone - Hearing Aid is a simple and transparent app that can come in handy for those in need of a hearing aid or an external mic.