Where a task requires the user to interact with more than one device, they need
to be aware of the seams: the different role of each device, and the point at
which the handover happens. This is especially important to help reinforce the
user’s mental model of the system, and what each part does. The less familiar
they are with it (e.g. during setup when devices are new and unfamiliar), the
more explanation is required. Below, we set out some key requirements for
effective, usable cross-device interactions.
In the first place, the user needs to know that they need to switch to another
device to complete their intended task. They may have to identify the correct
device from amongst several: for example, there may be several identical light
bulbs. Then they need to know what they’re being asked to do, and any
information that’s needed to interact effectively with the other device. They
also need to know why they’re being asked to switch. For example, are they
transferring data, or pairing the devices?
For example, the Misfit Shine syncing process tells the user to place or tap the
Shine on the iPhone screen (see figure 9.33). (Data is transferred over
Bluetooth LE but the sync is initiated by the phone recognizing the Shine on
the touchscreen).
Figure 9. 33 : Misfit Shine syncing
(https://www.youtube.com/watch?v=wmUOczrb9J4 -
http://i.ytimg.com/vi/wmUOczrb9J4/maxresdefault.jpg))
The Bluetooth pairing process to connect a Jaguar car to a smartphone displays
a 4 digit code on the dashboard that needs to be entered in the phone (if not
already displayed) (see figure 9.34). (See chapter 12, Key interactions, for
more on Bluetooth pairing interactions).