An app that is built using Android Studio and Java. Can be used to interface your android smartphone to a bluetooth device like HC-05 and transmit and receive data. It has 5 built in buttons that are mapped to control the direction of the motor(vehiche) in our case. But the buttons can be mapped to any values of choice by just long pressing and setting the value of them. The UI of the app looks like below.
Feel free to use the code and modify the contents according to your requirement. Also if anyone wants to modify or optimize the code can send their requests.