Used this in a store locator implementation. When the custom post type was saved, I grabbed the meta info ( address ) and used it to get the lat & long. through Google's geocode API.

Store Locator Geocode

add_action('save_post','my_update_shop');
/* add_action('post_updated','my_update_shop'); */
function my_update_shop($post_id){
  // Autosaves call this function but mess up the data saved to the DB, so we ignore them
	if( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ){
		return $post_id;
	}
	// Only go through if we're using the shop post type
	 if ( $_POST['post_type'] == 'shop'){
	 	// Set up the data from the meta boxes
	     $address =  $_POST['_cmb_shop_address']; 
	     $city 	 =  $_POST['_cmb_shop_city'];
	     $state	 =	$_POST['_cmb_shop_state'];
	     $zip     =  $_POST['_cmb_shop_zip'];
	     $phone	 = 	$_POST['_cmb_shop_phone'];
	     $website = 	$_POST['_cmb_shop_site'];
	     $title 	 =  get_the_title($post_id);
	     // Build the string from the address details entered
	     $requestString = $address.', '.$city.', '.$state.', '.$zip;
	     
	     // If the custom field is empty, the store is new and needs to be inserted
	     if( empty($_POST['_cmb_shop_lat']) ){ 
	     	// Make the request and put it in an array called coordinates	
	     	$coordinates = makeGeocodeRequest($requestString);
	     	$lat = $coordinates['latitude'];
	     	$lng = $coordinates['longitude'];
	     	insertStoreLocatorTable($post_id, $title, $lat, $lng, $requestString, $phone, $website);
	     }else{
	     // If it's not empty we should update it in case the address has changed
	     	// Make the request and put it in an array called coordinates	
	     	$coordinates = makeGeocodeRequest($requestString);
	     	$lat = $coordinates['latitude'];
	     	$lng = $coordinates['longitude'];
	     	updateStoreLocatorTable($post_id, $title, $lat, $lng, $requestString, $phone, $website);
	     }
	     // Save the lat and lng as post meta
	     $_POST['_cmb_shop_lat'] = $lat;
	     $_POST['_cmb_shop_lng'] = $lng;
	 
	 }
	 else{
	      return;
	 }
	 
}
/* Makes the curl call to google and returns the lat and lng in an array */
function makeGeocodeRequest($string){
	$string = str_replace(" ", "+", $string);
	$requestURL = "http://maps.googleapis.com/maps/api/geocode/json?address=".$string."&sensor=false";
	$ch = curl_init();
	curl_setopt($ch, CURLOPT_URL, $requestURL);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	$response = json_decode(curl_exec($ch), true);

	if($response['status'] != 'OK'){
		return null;
	}
	
	// Get the data from the response
	$geometry = $response['results'][0]['geometry'];
	$latitude = $geometry['location']['lat'];
	$longitude =  $geometry['location']['lng'];
	
	// Build the array to return
	$array = array(
		'latitude' => $latitude,
		'longitude' => $longitude
	);
	return $array;
}