Reminders are a new feature in the latest version of the Google Search app for Android. You can create reminders using voice search and Google Now will show notifications.
Now you can also create reminders from the desktop Google Search. When you search for things like [when is bonnaroo 2013?], [when is the first day of summer?], [halloween day], Google shows a link that says: “Remind me on Google Now”. Click that link and “Google Now will remind you 1 week before.” For now, notifications are only available in Google Search for Android.
{ via Search Engine Roundtable }