Energy efficient personal transportation requires fuel-efficient and route aware driving. Driving coaching systems can provide to drivers all the information and guidance that is needed to learn these skills. However, persuading drivers to change their driving behaviour is a challenging task. We identify functional, design, safety, and persuasive features for systems supporting fuel-efficiency. Moreover, we analyse how these features are supported by state-of-the-art systems targeting reduced fuel consumption. Finally, based on our analysis, we discuss open issues and opportunities for future development of fuel-efficiency support systems. The literature and the reviewed research in the present paper illustrate the needs for overall situation assessment and benefits of careful and multifaceted approach for systems design when it comes to eco-driving: an effective system will make use of a versatile design toolkit in order to obtain enduring behavioural results.