You can use this module with the following in your ~/.xmonad/xmonad.hs:
Enable it by including it in your logHook definition. Eg:
logHook = updatePointer Nearest
which will move the pointer to the nearest point of a newly focused window, or
logHook = updatePointer (Relative 0.5 0.5)
which will move the pointer to the center of a newly focused window.
To use this with an existing logHook, use >> :
logHook = dynamicLog
>> updatePointer (Relative 1 1)
which moves the pointer to the bottom-right corner of the focused window.