Tweenbots
I came across this and thought it was cool.
Tweenbots is part of a project initiated by Kacie Kinzer of ITP. Kacie writes;
Tweenbots are human-dependent robots that navigate the city with the help of pedestrians they encounter. Rolling at a constant speed, in a straight line, Tweenbots have a destination displayed on a flag, and rely on people they meet to read this flag and to aim them in the right direction to reach their goal.

