scenario,
you are driving to work every day, so you obviously don't need a navigation app open to show you the way, but you also want to be aware of police cars.

I was going to work one time and as soon as I plugged my phone into my car, google maps gave me a notification something like "work is 15 mins drive" which means it knows roughly when I leave for work and it is sure its work cause its the same time always.

so idea is, even when the user isn't using the app, Waze or google knows they are going to work, Waze should watch out if there are any police cars on the way and alert the user.