I promised another audience member who overheard to post an overview of our solution here - I'm sorry I haven't gotten to it until now!
This was made a while ago, meaning it's for Sitecore 8.2 and EXM 3.4 (update 2)
Creating a message type
First I needed to create a new message type. Since an SMS can only send text, I used Sitecore's TextMail as a base. First step is to make a new template in Sitecore, which has Sitecore's Plain Text Message as base template.
Having this template, I went ahead and created a message type in my project, including all the usual suspects. The "IsCorrectMessageItem" implementation uses the ID of my new template to identify the version.
public class SMS : TextMail
{
private readonly TextMailSource _curSource;
protected SMS(Item item) : base(item)
{
this._curSource = (base.Source as TextMailSource);
}
public new static bool IsCorrectMessageItem(Item item)
{
return ItemUtilExt.IsTemplateDescendant(item, "{185B8860-3DFE-4B9E-A5DD-04A2D7DF3EC2}");
}
public static SMS FromItemEx(Item item)
{
if (!SMS.IsCorrectMessageItem(item))
{
return null;
}
return new SMS(item);
}
public override string GetMessageBody(bool preview)
{
return _curSource.Body;
}
public override object Clone()
{
SMS sms = new SMS(base.InnerItem);
CloneFields(sms);
return sms;
}
}
