When its batteries were low, it found an outlet and plugged itself in. Most importantly, when it got desperately stuck it sent a text message to an engineer who could log on to a web portal and remotely get the robot rolling again. According to Willow Garage, that scenario only happened twice: "During the run, there were only two interventions: one to help the robot maneuver around a chair, and another to tell the robot where it was ("re-localization"). In both cases, the robot noticed there was an issue and sent a message for help, and the issue was resolved over the web." Two bugs in 139 km? Not bad.