Pre-boot authentication / geli-aware bootcode

[Robert Simmons]

I posted this question to security, but all I got back was the sound
of crickets...

Would it be possible to make FreeBSD's bootcode aware of geli encrypted volumes?

I would like to enter the password and begin decryption so that the
kernel and /boot are inside the encrypted volume.  Ideally the only
unencrypted area of the disk would be the gpt protected mbr and the
bootcode.

I know that Truecrypt is able to do something like this with its
truecrypt boot loader, is something like this possible with FreeBSD
without using Truecrypt?