This paper explores how mobile tools are used in everyday life and investigates the issues surrounding their usage, or indeed, their lack of usage. Personal computers support us in a wide range of our desk-bound activities, but there is still relatively little use of computer-based tools in other parts of our day-to-day lives. We hypothesise that this is because certain barriers-to-use exist that discourage their use in everyday environments, namely that the tools are not readily to hand at the time of need and/or that they distract the user's attention too much from the surrounding environment or main task at hand. We briefly present our concept of a Smartwatch -- a wrist-worn form of a general-purpose wearable computer -- that aims to overcome these barriers. However, we strongly believe that a prerequisite to the successful development of this, and other types of mobile devices, is a better understanding of the use, or disuse, of mobile tools in everyday life (including traditional and paper-based solutions). To gain this understanding we conducted a diary study in which a group of twelve volunteers recorded their usage of mobile tools over a period of 2 days. With the large volume of data that was collected we performed a qualitative analysis based on grounded theory techniques, resulting in a comprehensive and detailed picture of the use of mobile tools in everyday life. From this understanding we have drawn out nine key themes which we present in some detail in this paper, including: situational versus portability strategies, the mobility of information, new behaviours derived from mobile phone usage, the importance of creative expression, concern over privacy and security issues, and the demonstrated existence of the barriers-to-use.