Posted: August 20, 2012
Learn more about Google Now here - Google has a video explaining what it can do.
If you are using an ICS rom but still want to try Google Now, you are in luck, it is possible. Read about how to install Google Now on an ICS device over at xda-developers.
If you already have the SpazeDog Jelly Bean rom installed on your Nexus One, follow this link to xda-developers and download the latest version of the AROMA installer for Google Apps. Copy the zip file to your Nexus One's SD card.
Reboot the Nexus One into recovery → select "install from sdcard" → "choose zip from sdcard" → "gapps-jb-aromainstaller" (or whatever you named the zip you downloaded) as shown below.