I'm not only a dad but I'm an uncle too.  I've got nieces and nephews who have given up lying to Uncle Brett.  I told them that I can always tell when they're lying and they're always surprised when I can call them on it.  If only I had one of these...

Watch what happens when Jimmy Kimmel gives a kid a fake lie detector test.  What cracks me up is how quickly the answer changes when the lie detector buzzes to signal a lie.