Bad news... With corona, there is no way to do what you described. The main issue is that maps don't return touch events, although there are other issues as well.
I would recommend you read up in the API documention on native.newMapView to see what the sdk has built in for maps: http://docs.coronalabs.com/api/library/native/newMapView.html
The map support allows you to basically:
- set a maps "view", the area of earth it displays
- place markers at specific gps coords onto the map (by passing in gps coords acquired from the device for instance)
- detect a tap on a marker that has been placed
- allow the user to scroll and zoom the map
So maps don't return an event when you touch them (except markers already placed), which means you can't tell when the user touches a location (and can't tell pretty much anything they do with the map). In fact, with the current implementation of newMapView, you can't even tell where the mapView is displaying (you can set the initial gps coords for the view, but if the user scrolls, there's no way to tell where it is pointing).
So the maps are pretty limited on input (and also limited on getting basic status info like what the current view coords are). On the good news side, they're pretty easy to implement (see the coronaLabs sample programs), they are cross platform and will display on 1 billion+ devices out there in the marketplace...