On the way into work this morning I heard a radio ad for just such a program, which I think was called "ToGo" or some such Spanglish name. I just checked the App Store on my iPhone and found it, for $4.00.
There are a bunch of other apps available, just search "Santiago Chile maps" and they will pop up. Sorry but I can't recommend one over the others as I haven't used any of them. I do my local navigating with a Garmin GPS.