This helps you to connect any arduino to android phone with usb otg cable.It is very usefull method of communication between android and arduino.Most of the people use Bluetooth for this purpose but otg cable has more advantages than Bluetooth .
Advantages of USB OTG Cable over Bluetooth :
• OTG Cable is very cheap less than a dollar
• It consumes less power
• Easy to connect
• It is relatively fast than Bluetooth
Now a days robotics is one of the major field of science . Most of the robots can be made easily with arduino microcontroller .Arduino microcontroller is easy to use than pic or any other microcontroller. One of the reason is that it uses C language for compilation and most of the libraries are already built in the compiler.
Using Arduino with Android has many Application some them are mention below
1) Android Controlled CAR
2) Arduino Android Weather Station
3) Home Automation System
4) Line following Robot

Most Basic Algorithm that can be used to control robot from mobile is that send some character using this app let say ‘1’ to arduino then on arduino programming compare the received bit with ‘1’ if it is ‘1’ then perform some action .In this way send different character to arduino and compare with the corresponding character on arduino side .One can use if else or switch and case for comparing .
Arduino Code is provided inside the Application.