While Google had recently added Indian accents to the Google Now app, the app has received support for Hindi on the occasion of the Independence Day.
Google Now for Android now has support for Hindi for the voice search. Surprisingly, the app detects the Hindi phrases very accurately but slightly falls shorts due to the lack of adequate Hindi search results. The feature is apparently being rolled out in a phased manner and should soon be available to everyone.
To activate the Hindi voice search in Google Now, go to Settings and Voice in the Search and Now cards options. There the user can select Hindi as the default language. However as of now there is no support for the ‘Ok Google’ phrase in the language. Further, the app is said to soon support multiple primary languages.