Enviar SMS en Android (JAVA)

Primero agregamos el permiso en el AndroidManifest.xml arriba de la etiqueta application

<uses-permission android:name="android.permission.SEND_SMS" />

Mi manifest me quedó así:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.hector.simplemassivesms" >
    <uses-permission android:name="android.permission.SEND_SMS"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

Para enviar SMS hay dos vias:
Usando SmsManager:

SmsManager mySMS = SmsManager.getDefault();
String destination = "16501234567";
String msg = "Enviando mensaje!";
mySMS.sendTextMessage(destination, null, msg, null, null);


O usando intent

String SENT_SMS_FLAG = "SENT_SMS";
String DELIVER_SMS_FLAG = "DELIVER_SMS";

Intent sentIn = new Intent(SENT_SMS_FLAG);
PendingIntent sentPIn = PendingIntent.getBroadcast(this,0,sentIn,0);

Intent deliverIn = new Intent(SENT_SMS_FLAG);
PendingIntent deliverPIn
                   = PendingIntent.getBroadcast(this,0,deliverIn,0);