Talking Serial Monitor Android app
This handy app functions just like the Arduino IDE's Serial Monitor but in mobile way.
Users need to connect this app to Bluetooth modules (not over USB-OTG) such as Bluetooth Bee or HC-06 on the hardware side to start the serial monitoring job.
Talking Serial Monitor (Free Version): https://goo.gl/zxcMis
Serial Monitor for Arduino (Full Version): https://goo.gl/5dkDzP
Sample Visitor Counting Arduino code: https://goo.gl/1hzgDi
Circuit diagram for above project: https://goo.gl/1PFpam