The user interface automation tool in the Tools allows you to interact with the script with your user interface, take screenshots, or test valid answers along the way. These test scripts are written in JavaScript, which allows you to run fairly complex tests.
The tests that I ran were always directed, but I see no reason why you could not use something like the random () function to trigger random touch events, etc. From this, you could build your own monkey-like tool to slaughter your application. Even better, you could run other tools at the same time to identify potential memory leaks or processor hot spots.
I show how UI Automation works as part of a testing session in my iTunes U course , for which my notes can be viewed here .