Just in time to complete my time lapse kit, Switronix has announced a power cable that is compatible with all four Nikon cameras that support the EN-EL15 battery (V1,D7000,D600 and D800). The cable is compatible with their current battery packs (like this one) for an extended time out in the field with your camera using their built in intervalometer or recording video.
Switronix says that when paired with any of their V-mount or 3-Stud batteries you will get “HOURS of runtime”. I personally would love to see a graph or chart to shed a little more light on how long exactly theses products would run for because I am far too lazy for math. At this point there is no price shared but you can find the press release here and the XP-DSLR-EL15 product page here.