I was not aware of this project, but I have had a similar hardware setup half-completed on my workbench forever. I am using an old thinkpad T40 (love the keyboard, and it seems to be indestructible) with a serial connection to a RPi velcroed to the case. The laptop passes cyphertext and destination data only to the Rpi, which forwards it along and also does the reverse. My thoughts were that if I disable SLIP-type functionality on the laptop, along with all networking, that it would sufficiently isolate the laptop. Now you've got me thinking about 3 RPi-zeros packaged to fit in the CD drive slot...