Google Instant, unveiled for the desktop in September, is now ready for iPhone and Android users.

Google Instant has made its way to the mobile phone--at least two of them.

Google searchers in the U.S. using the iPhone and Android phones will start seeing Google Instant show up on their devices over the course of today, Google said in a blog post. It's a beta release, meaning Google doesn't want you to get mad at them if it doesn't work exactly right, and unlike the desktop version, you have to turn it on in order to see results as you type. It only works at Google.com in your mobile browser, but not in any of the other search boxes.

This is theoretically a boon to mobile searches, because typing on a mobile device is far more annoying than typing on a full-size keyboard. However, as TechCrunch notes, the limited screen real estate on a mobile device may make the service less useful. The keypad on several touch-screen mobile phones takes up nearly half the screen on its own, and the drop-down box that produces suggested Google Instant results further reduces the page available for the search results page itself.

You'll need to be running iOS 4.0 or Android 2.2 in order for this to work, Google said.