The Dev Team has the iPhone running unsigned applications. This was completed as part of their Pwnage Project which installs hacked firmware onto the iPhone, unlocking the iPhone and allowing the installation of both official and unofficial apps, and even patches.
Unfortunately, current Installer.app applications need to be modified: "they changed lots of the API, a lot. We will see how much has to be changed to the Toolchain [the previous development tool for iPhone independent developers] to still work after 2.0."
As quoted to Gizmodo: "the hacked 1.2 firmware works with anything. AT&T and others, it's pwned. And Apple will not really be able to patch it this time... somehow :-)"
If a video of the 2.0 Beta Firmware gets posted I will add it here. Otherwise you can take a look at the Pwnage Project on 1.1.4 here.