A Partition backup is possible, but its not designed for easy use. Isnt even an application, but a technique

Here is a how-could (like a how-to, but YMMV): http://metalab.at/wiki/Hack-A-N900/D...e_rootfs_Image

In the end, you will do backup with dd if=/dev/mtd5 | ssh root@yourlinuxpc "cat > rootfs.img"
and a restore with the flasher ./flasher-3.5 -r rootfs.img -f -R

But keep in mind that you are playing with bare data, so you must know what are you doing if something goes wrong