Detecting NSLU2 hardware?

[Marc Singer <elf@buici.com>]

I know that I can detect an NSLU2 by looking at /proc/cpuinfo and
checking the Hardware: line for the NSLU2 moniker.  I can also
detect whether or not APEX is installed on the system by calling
apex-env and checking for a release version, though this is a little
less reliable.  It is possible that there is another system
with APEX that isn't NSLU2, so I would rather not use that criteria.

Is there another, or perhaps a best way to detect the presence of
NSLU2 hardware?