I haven't done so much more. If you want more bugtesting just don't write that init string and you should get a console instead of memtester. If you want more info about memtester
http://pyropus.ca/software/memtester/ check it out there.

If you all want to know how I built it.

I created a small initrd containing busybox and the memtester tool.. after that I created a linuxrc. A boot script that takes the info from the /proc/cmdline. The info in the cmdline is the extra boot arguments like memtester=512.

after that i compiled a simple kernel with the initrd
like this

make zImage.initrd

after that it was all done.. not very hard.

If you really want the sources
http://www.kernel.org <- linux kernel
http://www.busybox.net <- busybox
http://pyropus.ca/software/memtester/ <- memtester tool

and btw. Mupper v1.1 will go into testing this week. this time I will release two separate version. A small one and a big one..