My other idea is doing it the way Qole's Easy Debian is made. Create virtual partion file, place it in EMMC or SD and use easy-chroot scripts to mount it in filesystem and use just like any other directory in your system. You could also build a custom filesystem with custom apps there (someone today announced here that he will maybe create specialized and customized Easy-Debian based image files for web developers - with LAMP, etc. - and for other use-cases if there is interest), I don't have the link now, but you can find it easily I guess. I have set up maemo sdk this way on my device (this is probably similar to DON900, haven't chacked) using custom ext2 image file and modified easy debian scripts, it's actually quite easy to do Qole has also some more images ready for chroot: http://qole.org/files/