There has actually been something similar (even, a serious and real product that has been actively maintained for years and is being sold for $1.99) in Cydia (for jailbroken iPhones) available on iOS for a while now, in case anyone wants to try it on non-Android ;P.
April fools or not, if we're talking alternative fast input methods then why not remind people of chording keyboards? Nice simple keypads ergonomically designed for comfortable one handed use with multi key combinations corresponding to letters / digits / symbols.
There was a trial a few years back by the University of Queensland marine division of an underwater system with HUD facemask display and a chording keypad so that researchers diving could hold specimans / tools whilst also looking up references / enter data.
Like a number of alternative key entry systems it was surprisingly fast once people became used to it.
Many high-speed CW (Morse) operators use devices with two inputs rather than one (called "iambic paddles"). See https://en.wikipedia.org/wiki/Telegraph_key for various types of Morse inputs beyond the traditional single key.
I find it kind of sadly ironic that morse code could actually speed up input, and perhaps shouldn't be treated as a joke. For example, a pair of telegraph operators beat "the world's fastest SMS texter" on Jay Leno a couple years back.