People are increasingly interacting with an ecology of devices that include smartwatches, smartphones, tablets and other traditional desktop-based devices. As a small wearable device, the smartwatch has the ability to become a central mediating device that instruments the human hand into a reconfigurable tool that provides other devices with personal access to users personal information, thus, mediating interaction between other devices. In this paper, we discuss a number of interaction techniques and applications that demonstrate how a smartwatch can allow for interaction within an ecology of devices. We summarize open challenges and describe directions for future work.