Quite simple. Do this:
0. Use a service that redirect SMS-messages to a mailaccount.
1. Create a gmail-account (or configure a Mail-accont to redirect mail from a certain user - your phone...)
2. Set it to redirect every mail to your WordPress installation. Make sure to configure the WordPress E-mail settings.
3. Send SMS to your G-mail account.
Now your SMS-messages will first go to your gmail, your gmail will auto-redirect it to WordPress and WordPress will publish it.
OR.. you could simply use your phones inbuilt mail function and mail directly to your WordPress installation.
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