<?php
$dbhost = 'localhost';
$dbuser = 'ubicaciones';
$dbpass = 'ubicaciones';

$conn = mysql_connect($dbhost, $dbuser, $dbpass) or die ('Error conectandose a mysql');

$dbname = 'ubicaciones';
mysql_select_db($dbname);
$query  = 'SELECT lat,lng FROM tracking ORDER BY id DESC';

$result = mysql_query($query);

$row = mysql_fetch_array($result, MYSQL_ASSOC);
    echo '{"lat":'.$row['lat'].',"lng":'.$row['lng'].'}';
mysql_close($conn);
?>