As Darrell reported, I now have one of his tools connected to my "spare"
digijet ECU and plugged into the FI system. Darrell is creative and very
competent with this electronic stuff(unlike myself). I learned a lot while
he patiently wired up the circuit board in the ECU.
I did experience some engine "stumbling" while driving in the rain
yesterday, which I suspect is weather-related and possibly a poor ground. I
noticed that with each episode of stumbling, both the fuel pump and coil
LED's flickered.  I will take a spin as soon as things dry up to verify the
moisture hypothesis.
I like the idea of using the information provided by the tool all the time,
rather than just to check out problems.  To that end, I agree with Darrell
that making the box somewhat smaller and running on 12-volt power with a
backlight would allow for easy mounting to the dash, possibly on the plastic
panel to the left rear of the shifter.
I recommend obtaining the digitool if you are interested in becoming more
informed about the FI system, which in my opinion, contibutes to peace of mind.