The Tamagotchi was this super cool handheld digital pet, created in Japan which certainly made it into my pocket growing up in Nairobi. Tamagotchis live inside in a small egg-shaped computer with an interface usually consisting of three buttons, although the number of buttons may vary for different variations.
Basically the object of the "game" was to see just how long you keep your pet alive. The pet goes through several distinct stages of development throughout its life cycle and can "die" due to poor care, old age, sickness, and in a few versions, predators.
I owned two and accidentally over fed one and he died. *Sigh* Not sure what happened to the other one. In these iPad days, they probably make them cooler these days.
Either way, good times :).