This app was mentioned in 1 comment, with an average of 3.00 upvotes
I know there is an app that does this already. I used to have it back when I was on Android but I can't remember the name. I'm looking for it now.
EDIT: It's the history channel app..not exactly what OP mentioned but does notify you of historical sites as you approach them: https://play.google.com/store/apps/details?id=com.aetn.history.android.historyhere&hl=en