During the 80s and 90s, a number of technology manufacturers produced hand-held PDA (Personal Digital Assistant) devices. CASIO made a number of them, including Credit Card form-factor PDAs. They could generally function as calculators, alarms, clocks, contact books, etc. These types of devices were later replaced with larger, touchscreen PDAs that are often called "Smart Phones."
One of these Credit Card form-factor PDAs was the CASIO DC-810. Released in 1988, it could function as a schedule, telephone book, alarm, and calculator. It originally came in a protective sleeve, but perhaps a 3D printed case would be better.