Khan Academy runs entirely in your browser and there is no special software required to use Khan Academy. As such, any device that can run a browser can be used to access Khan Academy. In the schools we work with we have seen the whole gamut including Laptops, Chromebooks, Netbooks, iPads and other tablet devices.
We recommend having a 1:1 student-to-computer ratio in the classroom at the time of use. Of course schools often share a laptop cart between classrooms. Some of the schools that we work with also have an open access policy where they let students bring in their own devices.