elgregI couldn't find any way to remove a point from a post (clearing out the various map fields just left it unchanged). I did some digging in the code and found the update_post function around line 945 could use an "else" on it's if($addr) statement. I also saw that there was some code at the top of the function for deleting the meta data and just dropped that in the else part (I'm guessing it was legacy code).
It works. Now the end up of my update_post function looks like this:
else{
delete_post_meta($id, '_geopress_id');
}
}