I modeled a first draft of the case we'll 3D print to house the battery and PCB for our device. Here are some screenshots:
The bottom of the case, with clips to hold it to the belt.
The top of the case. The upper compartment is to hold the PCB, and the lower compartment will hold the battery. The hole between the compartments is for running the wires for the battery. The gap in the wall of the PCB compartment is to expose the micro-USB connector.
The case from the side to show the shape of the clips.
The case lid, with a lip that will fit in the top of the PCB compartment.
This is just a first draft, and there's some things I need to improve. One idea we had is to have the battery be inserted through a larger hole in the PCB compartment, so that it's not exposed to the outside. We also want to have a switch that is engaged when the device is not being worn (i.e. when there's nothing in the belt clip). Our idea for that was to recess small buttons in the back surface of the case, and make the clips have posts on them that would actuate the buttons when the clips weren't being worn. However, I'm not sure how we would make this work, considering there wouldn't be a PCB surface to mount buttons to, and buttons of other mounting styles would be too bulky and deep. Other ideas we had for a "deadman" switch seemed too difficult to engineer in the time we have, and/or unreliable.