Kevin Schroeder has been working on a Zend Framework-based mobile application (Android) and ran up against a debugging issue that he would normally solve with features of his IDE, but since those weren't available on the device, he got a bit more creative.
The solution is similar to what I did with Debugging an RPC call in Zend Framework. What this does is set the cookies from the remote browser to debug on the local instance of the Zend debugger. To kick it off simply open up the URL to the debug kickoff page. That will set the cookies in your mobile browser. Then go to the page that you want to debug from your mobile phone and reload it.
He includes the code you'll need (a method to drop into your Controller) to make that debugging work. It sets up an array of cookie values and, when the page to debug is reloaded, those values will be set again and the IDE (in his case, Zend Studio) will catch them as a key to start debugging.