API to detect presence of keyboard and/or touchscreen
One very common pattern GNOME apps have is a Keyboard Shortcuts entry in primary menu that brings up the corresponding dialog. It doesn't really make sense to show it on mobile.
Similarly, there are things specific to touchscreen, such as overlay touch controls in a video game.
It would be very useful to have some kind of API exposed in libhandy for this so apps don't have to reimplement this logic.