MouseKeys

From ATWiki

MouseKeys is a generic name for a feature that is built into both Windows and the Macintosh operating system (therefore, most computer owners already have it) to allow a person to move the cursor with the number pad keys. For example, "8" moves the cursor up, "1" moves the cursor to the lower left, etc. MouseKeys provides a nice cursor control option for people who type with a mouthstick or typing splint. It is slow, but it offers good accuracy for times when a person needs to aim the cursor at a small target.

See the Mouse alternatives article for more cursor control options.