We can't even invent anti-virus software that doesn't raise false positives. Human communication is vastly more complex and variable. They'll not only need a sarcasm detector, but also an exaggeration meter, a satire alarm and an exhaustive colloquialism/slang/emoticon/typo translator.
For myself, I just prefer to randomly insert one of the monitored phrases on a regular basis. If everybody did that, they'd have to give up in frustration. Wouldn't they?
Anthrax
Megadeth
Slayer
Ding! Ding! Ding! Alert!