Our church staff was experiencing an issue where an attendee would text them and they thought they had sent a text back through Rock via the SMS conversations block, but the attendee never received the message due to their mobile phone not being SMS enabled. 

The SMS conversation block has a little pending message when the text hasn't sent, but staff are usually responding to a bunch of texts so as soon as they see the new blue message bubble they move on.

To help make it a bit more obvious that the person they think they are going to send a text to will not receive their message, I replaced the lava found in the SMS Conversations block settings for "Person Info Lava Template". It replaces the name with a link to the person's Rock profile, and it lets the user know if their mobile phone is SMS enabled or not.

Here is the lava:

<a href="/person/{{ Person.Id }}" target="_blank">{{ Person.FullName }}</a> {{ Person | PhoneNumber:'Mobile' }}

<br>

{% assign phoneNumbers = Person.PhoneNumbers %}

{% assign smsEnabled = false %}

{% for phoneNumber in phoneNumbers %}

    {% if phoneNumber.NumberTypeValue.Value == 'Mobile' and phoneNumber.IsMessagingEnabled %}

        {% assign smsEnabled = true %}

        {% break %}

    {% endif %}

{% endfor %}

{% if smsEnabled %}

    <label style="color:green;">SMS Enabled Mobile Phone</label>

{% else %}

    <label style="color:red;">THIS PHONE NUMBER IS NOT SMS ENABLED</label> 

{% endif %}