Despite the fact that Google Now in other forms has been out longer than Siri, it looks like Apple has added the service to its long list of lawsuits against Samsung, referring specifically to the Google Now functionality on the Galaxy S4. Here's a quote with some additional detail,
Apple has updated an earlier lawsuit filed against Samsung with claims that the Galaxy S4 and its Google Now feature violate two Apple patents covering functions of its own virtual personal assistant, Siri. Florian Mueller of FOSS Patents relayed news of the updated complaint on Wednesday, and he noted that two of the patents — U.S. Patent 8,086,604, and U.S. Patent 6,846,959 — cover technologies related to Siri. Both filings describe a “universal interface for retrieval of information in a computer system.” Apple also added three more patents to its earlier complaint that are not related to Siri, according to the report.
As you can see, Apple is up to its old tricks again. It's interesting that they are targeting Google Now on the SGS4, but not going after Google in the courts directly. Perhaps it's just a publicity stunt to convince people Apple had voice search and assistance first, even though it had been on Android for quite a bit longer. At this point it almost looks like Apple's lawyers are simply throwing stuff at the wall to see what they can get to stick.
Source: BGR