I have at least two that came to mind which inspired me to write this post:
1. A "sliding-grille display" calculator. I think I was somewhat inspired by the concept of Nixie tubes, where each digit was a discrete, physical component inside the tube, so I thought of this: imagine something akin to a normal desktop calculator (though perhaps a bit chunkier), but for each digit, rather than an LCD/LED/VFD element, or even a Nixie tube, there's instead a surface with a small strip of transparent cellophane or the like that wraps around both it and a stepper motor spindle behind the digit element. The surface has the digits 0-9 encoded in a lenticular fashion, and the transparent strip has stripes aligned such that, ideally, as the stepper motor actuates, it steps the strip along just enough to cover only the portions necessary to "reveal" a single digit encoded in this scheme. Obviously readability would suck on a device like this, and the logic needed to drive it would probably be heinously complex. :p
2. There was that one time I reinvented the concept of a dot-matrix teletype without realizing it.
I even had it all thought out with the idea of including both a normal dot-matrix head* and a white-out erasing head and such, with the idea being to try to simulate (within reason) what's possible on a video terminal/terminal emulator. Of course, having seen real dot-matrix printers and teletypes in action, I can see now why the concept would be less than practical. ^^;...anyone else had any similarly cool-yet-goofy ideas?
(* - ...sort of; what I was imagining was enough to print a full character in a single strike, rather than the single vertical row of pins a real dot-matrix printer has. Also, I think I was imagining an ink-imparting mechanism more akin to an inkjet printer rather than using a ribbon for some reason.)
