The guys of InstallerApps claim to have found an early version of Installer.app 4, the version that works with the iPhone 2.0. The download link works, but the installation process requires going through SSH and the command line.

This is apparently a beta rudimentary. So take all appropriate precautions adventure if you want to install it. As usual, is at your own risk and peril, and in case of problems, the Agency will deny having knowledge of your actions.