Many people with fine motor problems have trouble using the computer mouse. They lack the coordination to move the mouse effectively and then hold it still while clicking. The AutoHotkey program used in combination with a keyboard overlay can be used to simulate a mouse.
First, AutoHotkey is an open source (that is, free) program that allows the creation of macros in Windows. Macros can recreate any sequence of characters, function keys, and Ctrl and Alt keys that a user can type on a standard keyboard. AutoHotkey can also emulate mouse movement and clicking. Macros are assigned to keyboard hotkeys.
The mouse pointer can be moved in any direction in a range of speeds. Up, down, left, right and diagonal movement is possible. Mouse clicking and double clicking can also be emulated.
Second, on an overlay keyboard, similar to AutoHotkey, each key can be configured to play any sequence of keys on a keyboard. Unlike AutoHotkey, it cannot control the mouse by itself. However, a key can be configured to play an AutoHotkey hotkey that does control the mouse.
On an overlay keyboard, adjacent keys can be configured with the same key sequence. This can double, triple, quadruple or more the size of a key. Now those who lack fine motor skills have to hit a big key.
You can create a graphical overlay that labels what each key or group of keys does. The keys can be color-coded and include graphics such as arrows, making the keys easier to find.
One problem those who lack fine motor skills have with a standard keyboard is releasing a key before the repeat function kicks in. With an overlay keyboard, the repeat function is fully controllable. First, the repeat function can be completely disabled. Second, the time between repeating characters can be set to anything from fractions of a second to more than two minutes.
The combination of AutoHotkey and an overlay keyboard is a powerful combination. Especially when used to help those who lack fine motor skills.