iPhone hacker Niacin has just released his version of iBooter. Running on Mac, Windows and Linux, iBooter offers an interactive diagnostic and customization tool that talks directly with Apple's iPhone bootloader. With it you can set environmental variables, write a custom picture to the display (faboo if you're tired of that USB plug and the iTunes logo), run USB commands and diagnose why, for example, your iPhone isn't booting correctly.
Full installation instructions are available at the iBooter website as well as downloads for all three platforms. If you need to send commands directly to the baseband, iBooter is the tool you've been looking for.
