As the book is written, the sendSMS method will only send to the phone or emulator the app is running on. The fix for Android Studio Version 3.00 is to replace following code:
SmsManager sms = SmsManager.getDefault();

with the following code:
SmsManager sms = android.telephony.SmsManager.getDefault();

Rebuilding the app and loading the app to a phone allows the sms message to be sent to different phones :)