Well to my surprise I had already defined a "lastMessage" attribute in the child driver but never used it in the code below. I just wired it up to create an event for that attribute and it will store the last message sent so you can show on your dashboard.
Code is available in my Git repo. Since you are using the stock driver, mine is a bit different in that I have a parent "container" that allows you to create child devices so they all leverage the same Twilio API credentials. You will have to recreate your notification devices after installing the code but then you can link your rules over to the new devices and then remove your old ones.
@jshimota I also added this driver to HPM in case you prefer to install it that way.
