Combined apparatus for heating a fluid and for producing electrical power is comprised of a burner operable to burn a combustible fuel-air mixture to produce gaseous products of combustion; a heat exchanger adapted to receive the products of combustion and to transfer heat therefrom to the fluid; a gas-operated turbine; and an electrical generator that is co-rotatable with the turbine. The content of the web page may be automatically determined and then compared to content of the candidate advertisement to determine which candidate advertisement to select. Disclosed methods and systems consider a gestural vocabulary of a predefined number of user specified static andor dynamic hand gestures that are mapped with a database to convey messages. In some embodiments, the device is a peripheral of a computer system.