User trials of mobile applications have followed a steady march out of the lab, and progressively further ''into the wild', recently involving ''app store'-style releases of software to the general public. Yet from our experiences on these mass participation systems and a survey of the literature, we identify a number of reported difficulties. We propose a hybrid methodology that aims to address these, by combining a global software release with a concurrent local trial. A phone-based game, created to explore the uptake and use of ad hoc peer-to-peer networking, was evaluated using this new hybrid trial method, combining a small-scale local trial (11 users) with a ''mass participation' trial (over 10,000 users). Our hybrid method offers many benefits, allowing locally observed findings to be verified, patterns in globally collected data to be explained and addresses ethical issues raised by the mass participation approach. We note trends in the local trial that did not appear in the larger scale deployment, and which would therefore have led to misleading results were the application trialed using ''traditional' methods alone. Based on this study and previous experience, we provide a set of guidelines to researchers working in this area.

Field trials of experimental systems in the wild have developed into a standard method within HCI - testing new systems with groups of users in relatively unconstrained settings outside of the laboratory. In this paper we discuss methodological challenges in running user trials. Using a trial of trials we examined the practices of investigators and participants - documenting demand characteristics, where users adjust their behaviour to fit the expectations of those running the trial, the interdependence of how trials are run and the result they produce, and how trial results can be dependent on the insights of a subset of trial participants. We develop three strategies that researchers can use to leverage these challenges to run better trials.

This paper demonstrates how useful content can be generated as a by-product of an enjoyable mobile multiplayer game. In EyeSpy, players tag geographic locations with photos or text. By locating the places in which other players' tags were created and 'confirming' them, players earn points for themselves and verify the tags' locations. As a side effect of game-play, EyeSpy produces a collection of recognisable and findable geographic details, in the form of photographs and text tags, that can be repurposed to support navigation tasks. Two user trials of the game successfully produced an archive of geo-located photographs and tags, and in a follow-up experiment we compared performance in a navigation task using photographs from the game, with geo-referenced photos collected from the Flickr website. Our experiences with EyeSpy support reflection upon the design challenges presented by 'human computation' and the production of usable by-products through mobile game-play.

This paper investigates emergent practices around 'microblogging', changing and sharing status within a social group. We present results from a trial of 'Connecto', a phone based status and location sharing application that allows a group to 'tag' areas and have individuals' locations shared automatically on a mobile phone. In use the system moved beyond being an awareness tool to a way of continuing the ongoing 'story' of conversations within the group. Through sharing status and location the system supported each groups' ongoing repartee - a site for social exchange, enjoyment and friendship.

We introduce a location--based game called Feeding Yoshi that provides an example of seamful design, in which key characteristics of its underlying technologies-the coverage and security characteristics of WiFi-are exposed as a core element of gameplay. Feeding Yoshi is also a long--term, wide--area game, being played over a week between three different cities during an initial user study. The study, drawing on participant diaries and interviews, supported by observation and analysis of system logs, reveals players' reactions to the game. We see the different ways in which they embedded play into the patterns of their daily lives, augmenting existing practices and creating new ones, and observe the impact of varying location on both the ease and feel of play. We identify potential design extensions to Feeding Yoshi and conclude that seamful design provides a route to creating engaging experiences that are well adapted to their underlying technologies.

This paper presents a framework for the pervasive sharing of data using wireless networks. 'FarCry' uses the mobility of users to carry files between separated networks. Through a mix of ad-hoc and infrastructure-based wireless networking, files are transferred between users without their direct involvement. As users move to different locations, files are then transmitted on to other users, spreading and sharing information. We examine three applications of this framework. Each of these exploits the physically proximate nature of social gatherings. As people group together in, for example, business meetings and cafés, this can be taken as an indication of similar interests, e.g. in the same presentation or in a type of music. MediaNet affords sharing of media files between strangers or friends, MeetingNet shares business documents in meetings, and NewsNet shares RSS feeds between mobile users. NewsNet also develops the use of pre-emptive caching: collecting information from others not for oneself, but for the predicted later sharing with others. We offer observations on developing this system for a mobile, multi-user, multi-device environment.