There is a very useful application in the Android market called Zendesk that allows you to look at your Zendesk tickets on an Android powered smartphone. Use version 184.108.40.206 or higher. There may also be a version for the iphone on the Apps store.
Simply download the app and enter your credentials. The domain is abiquo.zendesk.com with your regular zendesk login.
There is also an app for iPhone/iPad available.
To complete the smartphone picture Zendesk have just announced a Windows Phone version.