I have been trying to build a GRUB2 package for OpenWRT with limited success. You can find the current results of my efforts at
http://morrowje.googlepages.com/grub2.tgz
It does not actually install grub2 onto the boot record of any image but merely builds the grub2 tools and installs them on the created image. From there, you'll have to do the rest manually. I created a script to help out.
One other issue is the matter of cross-compiling. I am building on 64-bit Ubuntu 8.10 for i386 and the build process errors out.
I am working on both of these issues but would be glad for any assistance!