Any chance you could do a teardown of what's inside the magic boxes? It seems to me that there must be some actual magic in the large magic box (and the small is essentially just wiring straight through).
I tried soldering on some $1.50 DC power connectors instead of paying $50 for the magic box. The cable from the battery to the laptop works perfectly, but the HyperJuice battery doesn't charge from the Macbook power adaptor - there must be something more required. Any insights into what the large magic box does would be appreciated :)