Lets be honest, one of the main reasons to be on Jelly Bean is the awesome new Voice Search feature. The improved accuracy and response time makes Voice Search the new Siri killer. Now you can simply say stuff like "Will it rain tomorrow" and Voice Search will figure out the correct response.
If you try to download Voice Search on a non-Jelly bean system, it will simply say "Your device is not compatible" and rejects the installation. Fortunately, rooted ICS users can get the app on their devices too using the steps below.
Steps to enable Google Voice Search on ICS Devices Requirement:
-ARMv7/ARMv6 devices only -You must be on a deodexed ROM(most custom roms are) Steps:
1) Download the zip file of the correct modded version of Google Now for your ARM device(see requirement - Links for ARMv6 and ARMv7)
2) Put the file in your SDcard.
3) Flash the zip in CWM. This will install Google Now into your app drawer
4) Install Google latitude installed set up the account for latitude
5) Open Google Now and go through the setup process. Click the "Yes, I'm in." option and your cards appear