Problem: 

People who use a touchscreen communication aid with a keyguard and have poor dexterity, but can put their finger into the keyguard holes to select cells, struggle to access the computer using the same method (since they can not select an area smaller than the keyguard).
 
Also, other people with dexterity problems might have difficulty clicking exactly on a button, but might be able to reliably click on an area of say 20x20pixels.
 
Further - people using mouse keys might want another method of selecting on the screen.
 
Solution(?):

ZoomClick software - every time you click the mouse, the software blows up a square of the screen every time you click. It then allows a second click on the 'blown up' area.  If the 2nd click is within the magnified area, the actual action is performed and magnifier closes. If the 2nd click is outside of the currently magnified area - then the magnified area is moved towards that 2nd click and no other action is performed

You can change the zoom factor.  A timer option shuts the zoom window after X seconds.

This is similar to what is used on some eye-gaze systems if you have seen them
 
Extension:

Grid the zoomed area (with thin visible lines) and number each grid so that

a) it can be used with a touch screen-keyguard and

b) someone can use a numberpad keyguard to progressively segment the screen into 9 and click this way (like in Dragon Dictate)

Simon (simon (dot) judge (at) nhs (dot) net )

Good idea Simon

The same sort of thing is currently available on some eye-gaze systems but I doublt whether they would release the code!  Mick Donegan spent some time persuading some of the developers in the COGAIN project to provide this.

David

This could provide a usable simple magnification solution where the user directs the point of magnification rather than it following their actions/events. It could do with some user testing. Would work best with a large pointer for non touch screen use.