If you can take a laptop through (or in fact any electronics) then in principle, this should be no problem.
Now this happened some years before the spread of home computers, and computer terminals were not a familiar sight to the average person. When the two friends got to the hospital, a guard stopped them and asked what they were carrying. They explained that they wanted to take a computer terminal to their friend who was a patient.
The guard got out his list of things that patients were permitted to have in their rooms: TV, radio, electric razor, typewriter, tape player, ... no computer terminals. Computer terminals weren't on the list, so the guard wouldn't let it in. Rules are rules, you know. (This guard was clearly a droid.)
Fair enough, said the two friends, and they left again. They were frustrated, of course, because they knew that the terminal was as harmless as a TV or anything else on the list... which gave them an idea.
The next day they returned, and the same thing happened: a guard stopped them and asked what they were carrying. They said: "This is a TV typewriter!" The guard was skeptical, so they plugged it in and demonstrated it. "See? You just type on the keyboard and what you type shows up on the TV screen." Now the guard didn't stop to think about how utterly useless a typewriter would be that didn't produce any paper copies of what you typed; but this was clearly a TV typewriter, no doubt about it. So he checked his list: "A TV is all right, a typewriter is all right ... okay, take it on in!"
[Historical note: Many years ago, "Popular Electronics" published solder-it-yourself plans for a TV typewriter. Despite the essential uselessness of the device, it was an enormously popular project. Steve Ciarcia, the man behind "Byte" magazine's "Circuit Cellar" feature, resurrected this ghost in one of his books of the early 1980s. He ascribed its popularity (no doubt correctly) to the feeling of power the builder could achieve by being able to decide himself what would be shown on the TV. --ESR]
[Antihistorical note: On September 23rd, 1992, the L.A. Times ran the following bit of filler:
Solomon Waters of Altadena, a 6-year-old first-grader, came home
from his first day of school and excitedly told his mother how he
had written on "a machine that looks like a computer -- but
without the TV screen." She asked him if it could have been a
"typewriter." "Yeah! Yeah!" he said. "That's what it was
called."
http://www.jargon.net/jargonfile/t/TVTypewriters.html
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If you went ahead and assumed that TSA agents are really just cleverly projected computer algorithms (androids perhaps?), your predictions concerning their behavior probably wouldn't be far off.
Fixed that for you.
This resulted in me being detained for over an hour while they ran every possible test on it, inspected every single item in my carry on and even photographing every individual page in my notebook. I was then followed until I got on the plane and even had to confirm that I was on the plane before it was cleared to depart.
This was on a US domestic flight. I have flown with prototypes in Europe several times (international flights) and have never had any problems.
Either way: bringing nonstandard electronics, even things that are much less sophisticated than acceptable things like laptops etc. can cause you major headaches when the TSA is involved.
I'm wondering if you'd be better off carrying prototypes in a separate, custom piece of luggage, like a Pelican case. Something that says 'this is expensive and important', rather than 'someone made this in a garage'.
I fully acknowledge that "custom" and "different" are not equivalent concepts, but well, that's the rationale.