What is proper way to get ETA (estimated time arrival) from any location to my current location

Question

Would like to know what is proper way to get ETA (estimated time arrival) from any location to my current location, in consideration the following situation:

a. ex.

Answer 1

I know this post is a bit old but in case someone is looking at the answer since iOS 7 Apple provide an API in MapKit in order to calculate all these info.

Here is a snippet of how to use this API

    MKDirectionsRequest *request = [[MKDirectionsRequest alloc] init];
    [request setSource:[MKMapItem mapItemForCurrentLocation]];
    [request setDestination:destination];
    [request setTransportType:MKDirectionsTransportTypeAutomobile];
    [request setRequestsAlternateRoutes:NO];
    MKDirections *directions = [[MKDirections alloc] initWithRequest:request];
    [directions calculateDirectionsWithCompletionHandler:^(MKDirectionsResponse *response, NSError *error) {
        if ( ! error && [response routes] > 0) {
            MKRoute *route = [[response routes] objectAtIndex:0];
            //route.distance  = The distance
            //route.expectedTravelTime = The ETA
        }
    }];