You could use a PHP class, such as Ben Alman's Simple PHP Proxy / Github.
It let's you redirect cross-domain URL's in a variety of ways, including the following method to  "change up" your User Agent....
user_agent - This value will be sent to the remote URL request as the
     `User-Agent:` HTTP request header. If omitted, the browser user agent
     will be passed through.
I use it to insert an iFrame - with the iPhone version of google voice - into any page, for example...
Some of the many other ways you can alter the request by using this script are...
   url - The remote URL resource to fetch. Any GET parameters to be passed
     through to the remote URL resource must be urlencoded in this parameter.
   mode - If mode=native, the response will be sent using the same content
     type and headers that the remote URL resource returned. If omitted, the
     response will be JSON (or JSONP). <Native requests> and <JSONP requests>
     are disabled by default, see <Configuration Options> for more information.
   callback - If specified, the response JSON will be wrapped in this named
     function call. This parameter and <JSONP requests> are disabled by
     default, see <Configuration Options> for more information.
   send_cookies - If send_cookies=1, all cookies will be forwarded through to
     the remote URL request.
   send_session - If send_session=1 and send_cookies=1, the SID cookie will be
     forwarded through to the remote URL request.
   full_headers - If a JSON request and full_headers=1, the JSON response will
     contain detailed header information.
   full_status - If a JSON request and full_status=1, the JSON response will
     contain detailed cURL status information, otherwise it will just contain
     the `http_code` property.