According to the official announcement,
What we have:The team has also created a multi-boot front end that lets users toggle between Apple's own operating system and an alternative platform, called OpeniBoot (pictured above).
What we have in openiboot (but hasn't been ported yet):
- Framebuffer driver
- Serial driver
- Serial over USB driver
- Interrupts, MMU, clock, etc.
What we don't have (yet!):
- Read-only support for the NAND
- Write support for the NAND
- Wireless networking
- Baseband support
That's just the start; the iPhone Dev Team is interested in porting Android to the iPhone; they even ask about Android porters in their announcement post.
Check out a demonstration video: