Mongoïd

Here is a snippet from @jmcopeland, gmaps4rails is just an include away:

 class Venue
  include Gmaps4rails::ActsAsGmappable
  include Mongoid::Document
  include Mongoid::Geo

  field :location, :type => Array, :geo => true, :lat => :latitude, :lng => :longitude

  geo_index :location
  ...
end

In the very near future there will be support for Mongoid::Geospatial, the successor of Mongoid::Geo - something like this (this example also includes geocoder integration):

 class Venue
  include Gmaps4rails::ActsAsGmappable
  include Mongoid::Document
  include Mongoid::Geospatial
  include Geocoder::Model::Mongoid

  after_create :perform_geocoding # attempt if enough address items are available

  # rake db:mongoid:create_indexes
  field :location,  type: Point,    spatial: {lat: :latitude, lng: :longitude, return_array: true }

  acts_as_gmappable :lat_lng_array => :location

  field :location, :type => Array, :geo => true, :lat => :latitude, :lng => :longitude

  # use geocoder indexing?
  geocoded_by :address_str, coordinates: :location, :skip_index => true

  embeds_one :address,  :as => :addressable

  delegate  :number, :street, :city, 
            :zip_code,  :region, :country,   
            :to => :address

  Address.location_fields.each do |field|
    meth_name = "#{field}="
    define_method meth_name do |value|
      self.address = Address.new unless self.address
      address.send(meth_name, value)
      perform_geocoding if respond_to? :perform_geocoding # perform geocode on any address change?
    end
  end

  def latitude
    perform_geocoding unless location
    location[0] if location
  end

  def longitude
    perform_geocoding unless location
    location[1] if location
  end

  def address_str
    "#{address.street}, #{address.city}, #{address.country}" 
  end  

  def perform_geocoding
    geocode if !location && address_geolocatable?
  end

  def address_geolocatable?
     address && !address.street.blank?
  end
end