But I already invented your little sister.

buhahaha

Anyhow,

A motivation sensing device. It works similarly to a lie detector except for a few changes. First, you don't have to hook it up to someone. It could be a little hand-held scanner, in a pair of glasses, etc. Secondly, it doesn't sense whether they're lying or not. It senses if they have malicious intentions in whatever they're doing or saying at any given time.

or

A baseball bat with built in gay-dar.

or

A food tree that grows food whenever you plant it, so nobody would ever have to go hungry again.

What is it they say about silence being golden?