In his video showing off his achievement, planetbeing says: "It's not really production quality yet. I'd say it's alpha quality. Um, but pretty much everything works." In his blog, he apparently includes the file needed to get this working on your phone.
Pre-built images and sources at http://graphite.sandslott.org:4080/pub/idroid/idroid-release-0.1a.tar.bz. Read the README. For generic openiboot instructions, there's plenty now that you can search for.
As for support for the iPhone 3G, it should be coming soon. However, the 3GS will take somewhat longer. With the work he has already done on this project, hopefully more people will contribute to get this project really cooking.
Image from AndroidandMe