People increasingly communicate with their mobile devices on the go. In the field, contexts vary and influence the users' internal state and behavior, which impacts the quality of interaction with mobile devices. In this work, we present results from a field study to assess typing behavior, stress and contextual characteristics. Our COCONUT toolkit tracks contextual and behavioral variables with apps and special hardware. We focus on the occurrence of typing errors, and confirm prior results in detail that people do not slow down for typing while walking, despite producing more typing slips. Furthermore, we show to which extent increased stress leads to an increase in typing errors.

Network testbeds are essential research tools that have been responsible for valuable network measurements and major advances in distributed systems research. However, no single testbed can satisfy the requirements of every research project, prompting continual efforts to develop new testbeds. The common practice is to re-implement functionality anew for each testbed. This work introduces a set of ready-to-use software components and interfaces called Tsumiki to help researchers to rapidly prototype custom networked testbeds without substantial effort. We derive Tsumiki's design using a set of component and interface design principles, and demonstrate that Tsumiki can be used to implement new, diverse, and useful testbeds. We detail a few such testbeds: a testbed composed of Android devices, a testbed that uses Docker for sandboxing, and a testbed that shares computation and storage resources among Facebook friends. A user study demonstrated that students with no prior experience with networked testbeds were able to use Tsumiki to create a testbed with new functionality and run an experiment on this testbed in under an hour. Furthermore, Tsumiki has been used in production in multiple testbeds, resulting in installations on tens of thousands of devices and use by thousands of researchers.