There is what’s essentially a Bluetooth keyboard, which you can compare to just about any device that that you can input text into. If you take people who are blind, for example, they typically use a screen reader and they typically operate the screen reader through a keyboard. If they pair the keyboard to their smartphone, they can simply use the standard key presses that they would use on a PC to navigate that smartphone, like the tab key the arrow keys, and the qwerty keyboard. This is the same generally for folks that are not blind but are keyboard only users who might have difficulty with the touchscreen functionality of smartphones or tablets, in order to bypass that and to simply use the keyboard instead.
