Official comment
This feature has been released. As of release number 3.0.661 you can include the merge field [Last Inbound SMS] in a notification email to yourself to see the most recent SMS message received.
Create a message with the merge fields you wish to identify the contact and the message:
Then, create a global Rule with the Trigger "SMS Received from Contact" and add the action under "Then Do This" to "Notify someone with an email" sending that email to yourself. It will be populated with the contact's information including the full text of their last SMS message to ONTRAPORT.
Added Dec. 22, 2016 - Now you can also send the SMS via a text message to any one of your ONTRAPORT Users:

