I am very interested in a usb flash drive that will be both bootable on metal as well and qemu bootable. I believe Qemu-puppy is doing this here:
http://www.erikveen.dds.nl/qemupuppy/

To be even more demanding, I have found it possible to run the same image in and Mac OSX Q (emu) application.

Let's add one more request-- an encrypted root filesystem, with /boot in the clear. Feraga.com has a project for this

Any interest?