DICE iPod Integration Kit - draining my 12V

I purchased the DICE iPod integration kit for my '06 prius... the kit with the "black box" that plugs into the AUX port on the back of the stereo, and then has a cable to connect with the iPod interface port. It seems to be the source of my 12V battery drain. Here's the scenario:

I have the DICE "black box" in my glove compartment, and I have left the prius parked in my garage for 4+ days, only to find the 12V completely drained. The iPod is not plugged into the DICE box. This has happened a few times, when I forget to unplug the DICE box from the stereo.

I have unplugged the DICE box from the stereo AUX port (by means of unplugging the cable from the stereo to DICE box marked 'Vechicle connector') and had the prius parked for 7+ days, with seemingly no battery drain.

Although I admit to not measuring the actual charge at either period, it is pretty obvious when it is drained.

Has anyone else experienced this behavior? perhaps I have a faulty DICE box? I would think with the stereo off the DICE box shouldn't consume power. I should do a measurement of sorts to confirm, but will have to research how that is done properly.

I am thinking of splicing into the power cable from the DICE box to the stereo and wiring an on/off switch since that would be easier than unplugging the cable every time I intend on leaving the car off for more than a day.