Google Now just keeps getting better, but sometimes Google leaves us to find the new features on our own, as seems to be the case with a new 'flight price monitor' card which has been added.
The card, spotted by Android Police, basically does exactly what it says on the tin. If you search for a flight through Google Flights then the search giant will send you an alert on Google Now if the price changes.
Or it might anyway. As Google hasn't announced the feature it's also not known whether it's rolled out to everyone yet or even whether a simple flight search is enough to trigger or it.
It does seem however that it's currently limited to searches on Google Flights, so if you're planning your trip elsewhere you're on your own.
- Field Trip is another recently added Google Now feature.