I have fetched the RFID tag value using an RFID reader and it is now in my Arduino's serial monitor. I have to send it to an Android app. I need help on how to do this.
I don't want to use Bluetooth.
The additions to an Android application to accept information from the outside word is not trivial. There are many choices to make. If On The Go USB is to be used you might decide to automatically launch a specific application based on the USB Device ID (I assume the FTDI chip's in this case). This involves XML files. The application it self will have to connect over the USB port. So the application will need to include many Android USB libraries. It appears the author of this project has already done all that.