A brainstorming list of the various ways digital devices can vary in capabilities, interface, etc. Responsive design (today) is primarily concerned with the physical size of the screen, and tentatively exploring the resolution of the screen.

gistfile1.txt

New generations of computing devices are changing the way we interact with digital content. These shifts are usually lumped under the "mobile" banner, but that's just one facet of the new world. Forward-thinking designers, developers, and strategists need to consider all of the following (and more!) when they plan for their users.

Screen (This depends on the physical device, or how it's being used)
 - Physical size
 - Perceived size
 - Resolution
 - Responsiveness
 - Fidelity

Alternative outputs
 - Audio output
 - Tactile feedback
 - Speech synthesis
 - Physical copies
 - Physical Braille copies

Inputs (This depends on the device but may vary if users add new inputs)
 - Keyboard
 - Touch/Stylus
 - Move-and-click (touchpad, mouse, trackball)
 - Gaming controllers
 - Voice control
 - Gesture (kinect, Google glass)
 - Physical sensors (tilt, GPS, temperature, etc)

Connectivity (This can depend on the device, or where/how a user's using it)
 - Raw speed
 - Metering/Transfer limits
 - Latency
 - Reliability

Mobility
 - Wearable/Implanted
 - Physically fixed (desktop computers, living room TVs, kiosks)
 - Pocket-sized + wireless
 - Transportable (laptops, large tablets)

Privacy
 - Visible to all present (projection screens, set-top internet)
 - Public (library computers, many office computers)
 - Concealable (handheld devices, laptops with polarized screens, etc)
 - Isolated (private spaces, hard to eavesdrop) 
 - Locked (secured against unauthorized use)

Performance/Capabilities (?)
 - Memory/Storage
 - Raw speed
 - Responsiveness of input device