I built a few devices for extremely cheap costs, for people with disabilities to navigate their environment safely (for the blind) and voice their needs (for the mute).
Ended up becoming an open source project that hardware hackers all over the world contributed to. Notably Frank Buss, was involved with rewriting and significantly improving the efficiecy of the codebase.
This is something I worked on during high school that bagged me a position as a finalist in IRIS National Science Fair ( The Indian version of ISEF ). I wrote and published a paper about it when I was 16. ( I'm not proud of it, was a bad journal )