SMS sent to caller when he CALLs you....

- no main.xml works in background so no application icon generated.

- give following permission in Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.PhoneCallSMS" android:versionCode="1" android:versionName="1.0">

    <uses-permission android:name="android.permission.RECEIVE_SMS" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_CONTACTS" />
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
    <uses-permission android:name="android.permission.RECEIVE_SMS"></uses-permission>
    <uses-permission android:name="android.permission.SEND_SMS"></uses-permission>

    <application android:icon="@drawable/icon" android:label="@string/app_name">
     
        <receiver android:name=".PhoneCallSMS">
            <intent-filter>
                <action android:name="android.intent.action.PHONE_STATE" />
            </intent-filter>
        </receiver>
       
    </application>
</manifest>

PhoneCallSMS.java

package com.PhoneCallSMS;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.telephony.TelephonyManager;
import android.telephony.gsm.SmsManager;
import android.util.Log;
import android.widget.Toast;

public class PhoneCallSMS extends BroadcastReceiver {
    //@SuppressWarnings("deprecation")
    @Override
    public void onReceive(Context context, Intent intent) {

        TelephonyManager telephony = (TelephonyManager) context
                .getSystemService(Context.TELEPHONY_SERVICE);
       
        if(telephony.getCallState() == TelephonyManager.CALL_STATE_RINGING)
        {
       
        Bundle bundle = intent.getExtras();
        String phone_number = bundle.getString("incoming_number");

        String message = "Sorry, I am busy...will call you back..!";
       
        SmsManager sms = SmsManager.getDefault();
        sms.sendTextMessage(phone_number, null, message, null, null);

        Log.e("Msg SENT", "SMS SENT TO RECEPIENT");

        Log.w("Incoming call", phone_number);
        Toast.makeText(context,
                "Hello,You have incoming call from..." + phone_number,
                Toast.LENGTH_LONG).show();
        }
    }
}