How to book the cheapest flight? Google it! Holidaymakers can now receive real time alerts as soon as holiday price drops (but only if you use Google Flights)

It can already tell you if your flight has been delayed, where you left your car and even wake you up before your station if you fall asleep on the train.

But Google Now's latest offering could change the way we book holidays forever.

It is now able to alert users searching for flights when prices change - with information based on their previous searches.

The service that already voluntarily offers people information about the their journey and upcoming appointments will make a note of any flight searches you make and let you know when the price of that journey changes.

For example, if you search for a flight from London to New York in October, Google will monitor the prices and alert you via Google Now if the price drops.

While other services such as Airfare Watchdog have flight alerts, Google's offering is instant, making it more convenient and less time consuming.

But here's the catch.

So far, the service - snappily titled the 'flight price monitor card' only works when holidaymakers search using Google Flights to search in the first instance.

So customers searching using other travel search engines such a Kayak, Skyscanner or Travel Supermarket cannot make use of the alerts.

To start using the feature, you'd need to browse Google Flights to trigger it.

Google Now previously displayed flight information based on confirmation emails, but as of now it will automatically monitor prices for flight searches done on Google Flights.

In May, Google announced that smartphones using its Google Now service will be offering something known as a ‘parking detector’.

The intelligent personal assistant, available within the Google Search mobile application for the Android and iOS operating systems, lists the address of the place where you last left your car.

It's worth noting that while Google seems to have your trip - flight booking to catching the correct train - covered, you will have to physically take the holiday yourself.