The PARCtab
The PARCtab is most easily operated with two hands: one to hold the tab, the other to use a passive stylus or a finger to touch the screen.
But since office workers often seem to have their hands full, we designed the tab so that three mechanical buttons fall beneath the fingers of the same hand that holds the tab, allowing one-handed use.
The device also includes a piezo-electric speaker so that applications can generate audio feedback