Sturdy version of http://www.thingiverse.com/thing:779159 .
Battery compartment for 8x AA batteries (lasts longer then a 9v cell, use rechargeable batteries to not exceed the 12v max).
Reset button is flush with case to minimize mistakes.
Don't forget support for the battery compartment.
The battery compartment could probably be remixed in to a storage compartment for the cables instead (with a lipo setup).