"Hey, I thought of that!"
ca. 1961, Pocket Calculator.
When I was about eight years old, I opened up a transistor ...
... and was surprised to find that the case was almost entirely empty --- just a tiny dot of silicon with some wires attached to it! I'd been fascinated by the desktop calculators at my father's office (huge, whirring things), and realized that an electronic equivalent could be built from transistors. When I saw how small a transistor could be, I imagined a calculator built on a glass plate, with fine wires connecting the transistors, and with capacitance sensors for a keypad (so that it could be built without moving parts). I was not the only person thinking along these lines!
1971, Geometry Toy. I had a great time learning geometry in high school; Miss Sharman was the greatest! I realized that when I did geometrical proofs and constructions, the picture I had in my head was of a flexible model that could be moved through all the possible cases. I talked to Miss Sharman about making wooden models to make these things more real; she said she thought it was a good idea. When I first got involved with computers, I realized that a physical model wasn't necessary -- you could make it on a computer screen. I put this on my list of "got to work on this sometime" projects. Key Curriculum Press beat me to it -- and did a very nice job with their Geometer's Sketchpad.
1979, Crescendo-ing Alarm Clock. Starts with a gentle, inaudible "whoosh" noise, which increases slowly over a period of several minutes into gentle waves, then wind, and finally a deafening storm.