This app can be used for communication between your Android device, and any microcontroller (like Arduino or PIC) using a module like the HC-05 or HC-06.

The application has a terminal for viewing the received text from the microcontroller (ASCII printable characters), as well as programmable buttons for sending frequently used commands.
It also supports the option of appending a carriage return (\r) and newline characters (\n) at the end of the sent data.