Google's Instant search service is now up and running on its mobile sites as well -- when you hit up google.com on your iPhone or iPad's Mobile Safari browser, you'll see search results appear as you type your query in. You may have to reload the page once or twice; when you see the line "Instant (beta) is off: Turn On" you need to click Turn On to activate Instant.
As you may know from using instant search in other browsers, this is more of an average time saver than anything really revolutionary (and in some cases, I've even been bothered by early search results that weren't anywhere near what I was actually looking for). But anyone who really dislikes it can turn it off, and fans of the service should be happy to see it running on Mobile Safari.
Happy, that is, when they use the actual site -- note that since this is only a feature on Google's site and not actually built into the browser's search field, you still won't get instant search results when searching from Safari's own title bar search. Still, if you happen to be searching Google after that initial search, it will probably be helpful to save that second and a half or so while you're still typing the query in.