We investigate emergent effects in collaborative indoor localisation as an example of self-organisation in ubiquitous sensing systems. We consider pedestrian dead reckoning (PDR) systems that collaborate to improve their location estimate when two users are detected to be close to each other. In a simulation based on empirically determined parameters we discover two qualitatively different regimes of 'location awareness'. We show that as the frequency of collaborative improvements increases the system makes a transition from a state where the error of each device is unbounded to a state where the averaged maximum error is constant, i.e., location awareness suddenly emerges even though the individual mobile devices are by themselves not capable of exact location and have a tendency to accumulate error without bounds.