Okay, so I'm missing something (and I did read the README and search the forums).
I debootstrapped Jaunty onto a partition on my system and set it up with chroot from deblet. Everything seems to work great through chroot, but I can't get it to boot with bootmenu. The rootfs is on mmcblk0p1 (external MMC first partition) and I've set up fstab but I'm not sure if it needs to say /dev/mtdblock4 or /dev/mtdblock3 for the rootfs (I think it ought to be mtdblock4) as well as setting up a swap.
I tried the original bootmenu.d setting from the deblet bootmenu install as well as the new pb tools...deblet is still working fine, but I'm pretty sure I'm missing something... Do I need to setup /mnt/initfs on the Jaunty partition to make this work?