Today I've posted some patches that add SD/MMC card support to GNU parted, including libparted. It's actually just support for auto-detecting the /dev/mmcblk* devices, since the actual partitioning and block layer access of SD storage cards is exactly the same like on any other disk.
This has been fun, as I always like to read source code of programs that I've only been using so far ;). Luckily, the architecture is nice and abstract so the feature was easy to implement.
After the copyright assignment to the FSF has been done, the code will get merged. Once libparted has support for this, debian-installer should more or less automatically offer those devices as installation targets.
Now I just have to find out what the other distributions use for this purpose, with some luck they also rely on libparted and I don't have to implement this feature 5 times.