I have written a simple beginning to a Startup Disk util for linux, i call
PRAMBoot.  It has 3 boot partition options hardcoded, which should be modified
to fit your system.  I have them set up to boot MacOS, linux, and a safe backup
linux.  The location code is a 16 bit representation of the location of the boot
partition.  I'm not sure what they mean, but running this program with no params
will read what it currently is set to.  This works with my PDQ, and i dont know
if it will work with any others.  Requires nvram support.

I dont know if anything like this already exists.
I wrote this because i got tired of having to modify my miboot partition to boot
macos.

Also available at http://www.execpc.com/~jpgarcia

--
Joseph P. Garcia      jpgarcia@execpc.com      jpgarcia@lidar.ssec.wisc.edu
CS Undergraduate                      Student Employee - Systems Programmer
University of Wisconsin - Madison                            UW Lidar Group

"Ask yourself, Why do you seek the developer kernel?  Is it for its glory,
 or for yours?"