A free program for Android, by SAAPP Developers.
The best part about this app is that it’s really simple. You just have to connect your phone to the speaker, and you’re good to go.
Once you’re connected, you can use your phone as a microphone to make a loud announcement. You can record the audio, so you can play it back later.
It works with Bluetooth, so you can make an announcement in a variety of places, like in a cafe or a restaurant. You can also use it for presentations or lectures.