"I need to know something. The way we used to be together. I don't mean lately, but before, it was real, wasn't it?"
A good preventative measure for drunk-dialing would be a timelock on your phone, or maybe a breathalyzer. But even better than that would be a function on your phone that makes it so that if you call an ex after 3 a.m., you don't get connected, but instead your ex just hears that line of dialogue, backed by Phil Collins' "In the Air Tonight."
A foolproof plan sure to have every ex saying, "You bet it was."