Well first of all obviously you need to be able to send a picture via sms, which isn’t possible as far as I am aware. If you have the ability to send an MMS or email from your phone then set up a specific blog email address (ie, don’t give the address out to everyone) and look at how to get WP to check that email address for new mail to post.
The email server needs to support pop3, or have a look at https://economysizegeek.com/wp-mail/ I installed postie from there yesterday and it checks my gmail account every five minutes or so, I’ve posted a photo and a video from my phone, works fine. Doesn’t cost me anything except the cost of the mms from my phone, and I get a certain amount free anyway.
Hope that helps.
