I'm not entirely sure what you intended.
There are several problems.
In order to test the led at all we have to running on the firebox itself but neither of the boxes I have have video out so it has to be a headless distro/install.
We have the watchguard kernel module but it's a compiled binary built against the watchguard os which is kernel 2.4.26.
The Watchguard OS itself is heavily locked down. As it should be for a security appliance.
I've never tried chrooting into a filesystem but I would assume it has to be the same kernel version?
I'm open to suggestions. I started off running OpenWRT on the box and trying to setup a toolchain to compile for it on another box. The current OpenrWRT is 2.6 kernel though. Might be worth checking out older versions though. Hmm.
I spent a long while trying to get a real prompt on the Watchguard OS but after hours of trying I realised that even if I did I'd need to write a program to scan the IO ports while switching the LED and I can't compile for their custom kernel. It's basically Red Hat by the way.
The best solution I have come up with is simply compiling for pFSense on a FreeBSD box which works great. Playing around with the work of others (see the DD-WRT Firebox II thread) and modifying the code for FreeBSD I have soem basic code for reading and writing to address space. It works well for basic stuff like switching the back light on the LCD (parallel port strobe line, 0x379 bit 1). Not found the arm led on the parallel port though, would be too easy!
I was considering whether or not the arm/disarm led is likely to be at the same location across the range of models? Certainly not the same place as the Firebox II/III. However those models were from before Watchguard bought out Rapidstream.