Aside from having a physical keyboard in front of you, what other applications exist for keyboards with assistive technologies?

We see a lot of keyboard accessibility usage in kiosks. If you've been in an airport and seen a kiosk, those are all accessible from just the keyboard. The keyboard navigation criterion is also applicable to mobile devices. While mobile devices have touchscreen keyboards, some people don't rely on them, either by preference or because of their disability. You need to ensure keyboard navigation in those spots as well.