A self-propelled device for locomotion through a lumen, comprising a set of serially arranged inflatable chambers, and incorporating a number of novel aspects. To enable easy insertion and use, the rigidity of the device is increased by means of rigid inserts in the balloons, or by use of stiff springs between segments. The working channel can be attached to the distal chamber of the device, such that it is pulled from the leading end of the device during inflation, rather than being pulled from the trailing end of the device during deflation. Lumen wall inspection or treatment facilities are enabled by means of a camera or treatment arm mounted between two distally positioned balloons, the device is able to provide observation capabilities to the lumen wall, yet without becoming excessively dirty by exposure to the front end of the device, as in prior art camera units.