I apologize for being late, but here it is:
SMS Undo is a feature that apparently “undos” a text once it has been sent. I wasn’t aware of this feature myself because nobody ever talked about it before. I believe we should enable having an “undo” feature in the phone from the start, rather than having to search for an app. As Rose puts it, why not simply take most of the old features from older phones and install them in the smart phones? Apparently some old phones already had this feature.