There's a line of Casio calculators which has a dot-matrix LCD display and a 8-bit CPU of an obscure architecture called nX-U8/100.
Eventually, a way to make the Harvard-architecture CPU jump to arbitrary locations was discovered, and this combined with a manually dumped ROM image allows to execute arbitrary code using ROP.
The method of achieving a buffer overflow was originally discovered by a small group of calculator hackers on Baidu and that discovery makes the above possible.
Our research on casiocalc.org
has yielded the necessary documentation on the rare CPU and its architecture, and we plan on writing a custom loader to make this exploit more convenient to use. We have also developed an open-source emulator for the calculator to aid research.