Google Instant for mobile is now available for Android 2.2 ("Froyo") and iOS 4 devices in the U.S. in English.
To try it out, go to google.com in your phone's browser and tap Google Instant "Turn on" link beneath the search box (if you don't see "Turn on" link, try waiting a moment and then refresh the page).
"With Google Instant on mobile, we're pushing the limits of mobile browsers and wireless networks. You'll probably notice a big improvement in speed when you search thanks to a new AJAX and HTML5 implementation for mobile that dynamically updates the page with new results and eliminates the need to load a new page for each query.
Google Instant for mobile works best on 3G and WiFi networks, but since the quality of any wireless connection can fluctuate, we've made it easy to enable or disable Google Instant without ever leaving the page. Just tap "Turn on" or "Turn off" link," stated Google.