Before smartphones, there were personal digital assistants like the Palm Pilot, Handspring Visor, and Compaq/HP iPAQ line of devices. And before that, there is real basic PDAs, such as the Psion Organizer, which basically have a variety of features that you can also find in a calculator watch.
While you can find one of the old-school organizers on eBay, YouTuber Volos Projects decided to build one from scratch using an Arduino Nano, a custom printed circuit board, and a small OLED display.
The Arduino Pocket Computer is not exactly as powerful as modern computer standards. But it has all the features you’d find in a digital organizer from the 1980s or early 90s, including a phone book, calendar, stopwatch, calculator, and support for some basic games.
It may not be realistic to expect a handheld computer powered by an Arduino Nano to be able to do much more than that. It is a small board with a 16 MHz ATmega328 microcontroller 32KB of flash memory, and 2KB of SRAM.
The Arduino Pocket Computer can be impractical (the small display is barely large enough to display games or calendar appointments, and the exposed components can clog your pocket if you try to carry it. thing with you). But this is an impressive DIY project, and if you want to try making your own Volos post links you can use to order a printed circuit board to illustrate the video on YouTube, and you will find the code for the software running. on the GitHub device.
via the Arduino Blog