Encrypted SD Cards and Android?

Android's related to the Linux codebase (Google's supposedly even trying to merge the code back into the general Linux tree). Linux has some support for encrypted filesystems. I wonder if we can ever expect an Android app that would allow plugged-in SD cards to be written to using a Linux-compatible encrypted FS? I mean, it's great that my BB lets me password protect my phone. However, if someone kites my phone, they can still read anything stored on that 8GB micro SD card in it. If I could find a highly-securable phone (down to removable storage), I think that would be the phone I'd choose to buy.