Here's how you can download the SMS Backup + app free for Android devices.
1. Go to the Google Play page for the free app SMS Backup +.
2. Tap the Install button.
Here's a description of SMS Backup +:
"Automatically backup SMS, MMS and call log entries using a separate label in Gmail / Google Calendar. It is also possible to restore SMS and call log entries back to the phone (MMS not supported yet).
Remember to enable IMAP in Gmail."