Google announced that Google Now, the predictive search feature from Google, is now available on iOS devices. You can download it by just downloading or upgrading the Google Search App via iTunes App Store.
Once you do, to activate it, you need to load the app and agree to the prompts. Note, when you do that, you will notice that the GPS indicator is always on. The app constantly polls your location, so that Google can serve you predictive search results. I should note, this may have a battery performance implication to your device.
If you want to turn that off, you can, but it will prevent Google Now from doing its thing. Here is how to stop it:
Here is how Google Now works:
I've been playing with it all day yesterday and honestly, it is not pulling calendar events properly for me, it is not giving me traffic information on the way to or from work/home. It is not really working as I expected, why? Maybe because I am on a Google Apps account? I am not sure. Or maybe I am expecting too much.
Update: Spoke to Google. In short, the method they use for detecting your location doesn't use excessive battery (it uses wifi and cell towers, not GPS), plus Google Now gets better over time as it learns your usage and behavior. So time will tell.