The technologies exist now to develop wearable computers. Anyone with a few thousand dollars can purchase commercially available components, repackage the computer, add a head mounted display and build one. Wearable computer systems still have many user interface problems associated with them from both an input and output perspective. If wearable computers are to succeed major advances will need to be made in the way the user of the computer interacts with the system. This paper will discuss the construction of two wearable computer systems and some of the user interface and usability problems associated with them.