the solution to your request is Input Method.
what you have described is something familiar to most CJK language users.
let's review how input method works in current Linux systems.
Here's a simple architecture for a common input method system:
NOTE: I snapshot this image from The X Input Method Protocol. some of the arrows are irelevant to following discussion.
(historically, XIM (the X Input Method protocol) was the only protocol existed. it's overly complex and lacks some desired features. so it's mostly abandoned, though compatibilty is still provided by popular toolkits like GTK, Qt.)
an modern input method systemcontains serveral parts:
1. client side library support
typically implemented as a module loaded by toolkits. e.g. for GTK, see /usr/lib/x86_64-linux-gnu/gtk-3.0/3.0.0/immodules/
2. input method server
3. X server
how these parts fit together?
a user types a key. X server receives the hardware event from evdev interface, composes a XEvent and sends to the application under keyboard focus. the application toolkit(GTK, Qt) input method module intercepts the event and passed the info to input method server.
the input method server figures what the user may want and passes some text back to the IM module.
now let's talk about the architecture of the IM server.
a IM server typically consists of two parts:
1. a IM framework which handles platform specific intricacies and provides a nice interface to IM engine and toolkit IM modules. it provides the IPC mechanisms used by IM
module, IM server and IM engine.
2. various IM engines do the actual work of transforming user-typed keys to desired text.
IM engines can be shared libraries loaded by IM server or independent processes communicating to the IM server.
3. auxilary input method configuration programs provides friendly user interface for customizing IM server and engine behaviors.
all in all, what IM does is to transform what you type to something diffent and optionally provide predictions.
here's is an example:
we use ibus-pinyin here to type some chinese characters.
the romanization of 汉语拼音 is 'han yu pin yin'. at first you need to type all these letters to get the four chinese characters. but after a few times, you just need to type the four initial characters 'h y p y' to get the chinese character.
in the ibus-pinyin case, 'han yu pin yin' is shortened to 'h y p y'.
more advanced IM engines utilize statistical learning techniques to provide better prediction.
nothing can stop you from writing a english input method engine to provide typing boost.
as a bonus, all toolkits have input method support except some plain old X programs. so this is a quite universal solution.
Thanks to Anders F. U. Kiær. http://fedoraproject.org/wiki/Features/Typing-Booster should be the answer