any item, piece of equipment, or product system, whether acquired commercially off the shelf, modified, or customized, that is used to increase, maintain, or improve functional capabilities of a child with a disability.
IDEA also defines assistive technology services as:
any service that directly assists a child with a disability in the selection, acquisition, or use of an assistive technology device. Such term includes--
(A) the evaluation of the needs of such child, including a functional evaluation of the child in the child's customary environment;
(B) purchasing, leasing, or otherwise providing for the acquisition of assistive technology devices by such child;
(C) selecting, designing, fitting, customizing, adapting, applying, maintaining, repairing, or replacing assistive technology devices;
(D) coordinating and using other therapies, interventions, or services with assistive technology devices, such as those associated with existing education and rehabilitation plans and programs;
(E) training or technical assistance for such child, or, where appropriate, the family of such child; and
(F) training or technical assistance for professionals (including individuals providing education and rehabilitation services), employers, or other individuals who provide services to, employ, or are otherwise substantially involved in the major life functions of such child.