Long-distance human-robot collaborative tasks require robust forms of knowledge-sharing among agents in order to optimize the performance of the task. In this paper, we propose to take advantage of the proliferation of mobile phones to use them as a reliable low-cost communication interface, as opposed to the use of specific gadgets or speech and gesture recognition techniques that are highly prone to failure in the presence of noise or occlusions. Our interface is focused on search tasks, and it allows the user to share with the other agents real-time information such as their position, their intention or even what they would like the other agents to do. To test its acceptability, a user study was conducted with 20 volunteers in a human-human scenario. A second round of experiments with other 30 volunteers was conducted to test different ways to encourage user interaction with our interface. Finally, real-life experiments were also conducted with a robot to apply skills learned to the desired scenario. We found a statistically significant improvement in the amount of information exchanged between agents.