If computer monitors can [?] to almost nothing, why [?] keyboards? They soon may. [?] companies have developed prototype "[?]" keyboards designed to accompany [?] devices like PDAs, tablet [?] and cell phones. Here's [?] they work: a laser [?] projects a glowing red [?] of a keyboard on desk or other flat [?]. A sensor like those [?] in digital cameras monitors [?] reflection of an infrared [?] projected on the same [?]. It can tell which "[?]" you are trying to [?] by the way that [?] changes. Someday, similar keyboards [?] be built into the [?] they work with, so [?] they disappear when not [?] use.