Android only: Google's scribble-powered Gesture Search is pretty handy, but you have to launch a separate app to access it. Free app Gesture Search Bar more conveniently launches Gesture Search from either your notification bar or by long-pressing the Search button.
And... that's what Gesture Search Bar does, in whole, but it makes Gesture Search more of a system utility than a neat toy to show your friends. If you decide later you don't like Gesture Search taking over your search button (and replacing the Voice Input default), head into your Setings -> Applications, choose the All tab, then head into Gesture Search Bar and click "Clear Defaults".
Gesture Search Bar is a free download for Android phones. You can grab it using the QR code at right.