Minimal output display (LED-based)
Similar to the no-display wearables but with a little bit more visual feedback are the minimal-display wearables. These devices incorporate a small LED or OLED display, which displays on-device selected information that is critical to the experience. This display is not interactive: it’s one-directional, outputting information for the user to view, but the user doesn’t actively interact with it nor can the user enter any input.
Activity and health trackers currently dominate this wearables group, as well, offering to the wearer visual feedback on their progress. This feedback can take several forms:
A set of lights that provide a rough indication to the user about her daily activity progress. Figure 4-18 shows Fitbit Flex and Misfit Shine, two examples of this kind of minimal display. The lights illuminate automatically when the user reaches her daily goal (all lighting up festively, usually accompanied by vibration feedback). Additionally, the user can manually ask to see her progress status by clicking a button or performing a gesture (for instance, a double-tap on the wearable surface), which turns on the relative number of lights, based on the progress.
Figure 4-18. Fitbit Flex (top) and Misfit Shine provide light-based visual feedback on the wearable device
Similarly, you can also use a single light (turning on/off, or changing colors) to reflect different key experience states. One good example is CSR’s Bluetooth smart necklace, mentioned earlier in the chapter. It uses a smart LED which illuminates when a smartphone notification arrives. In fact, the user can customize the light to display different colors for different kinds of notifications. Figure 4-19 shows another example, the Mio LINK, a heart rate monitor, which offers just a single status LED.
Figure 4-19. Mio LINK, which uses a single on-device LED to provide feedback about the heart rate state
Mio LINK comes with a complementary smartphone app, Mio GO, which offers extended data as well as a second-screen companion during indoors workout by recreating landscapes and trails via video footage on the tablet screen.
The LED-based wearable UI keeps the display minimal and clean. Such a display is limited in terms of data, but it facilitates designing more fashionable, elegant-looking wearables. In other words, in the fashion-function balance, more weight is put on the design. Additional data and functionality is provided on the companion apps, similar to the no-display wearables.