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Smart devices communicating with each other are pervading our society. Their applicability spans a wide range of domains, from wireless sensors deployed in space or military zones to cameras, cars, and refrigerators. Transportation, communication, medicine, commerce, and banking are all areas increasingly embedding IT (Royal Academy, 2009), and gradually promoting the use of smart, typically small, IT-based devices. We are becoming dependent on a very flexible living manner in which plane tickets can be ordered from a mobile phone that can also perform Internet banking and in the near future will act as an electronic wallet. The importance and versatility of such smart devices require them to work continuously and at full capacity. These characteristics are usually referred by Laprie, Avizienis, and Kopetz (1992) as reliability - the property of a system to continuously provide service and availability - the readiness for correct service of the system.
One often overlooked factor required for reliable and available systems is that of power or energy. This factor could be overlooked in the past where most communicating devices were stationary and electrically plugged machines. However, it cannot be ignored in the current networking environment that becomes context- and location-aware, (Yan & Sere, 2004; Roman, Julien, & Payton, 2004), hence it involves mobile, unplugged devices functioning on batteries. These mobile devices have numerous user-friendly features (Michael, 2005) such as high resolution display, radio, camera, TV, GPS, etc. At the same time, a device should be as small as possible, leaving not much space for the battery in spite of the increased energy need of its various features.
We can regard energy in relation to smart devices in a multitude of ways. One aspect is that of being provided by a battery, hence the engineering challenge of fitting a (rechargeable) battery supporting the functionality of the device and thus enabling mobility. Based on this aspect, users can question how long can a certain battery-enabled device be used and how flexible this usage is. For instance, if an individual travels to a remote location and there takes a very special trip, this person may need for the trip only the camera and the phone functionality of a smart device. The rest of the features - software and hardware - should be turned off to save the battery. The current smart devices are sometimes so complex that they do not offer such simple choices to the user. Instead, they may be running some antivirus software periodically, checking for updates, or loading and keeping a multimedia player ready to be used without a clear choice for the user on whether these features are needed or not. Yet another aspect concerning energy in relation to smart devices is that of deploying or developing products that consume no more than a certain amount of energy per time unit. Recharging a battery is another fundamental issue to consider as well. A clear implication of these energy-related aspects is that we need to take energy into consideration when developing and deploying smart devices: they need to be energy-aware.