Most of the editors I know work off the MacBook pro laptops, so I thought some people might find this information useful. Apple has patented and has been very protective about their MagSafe connector and has even sued a company for using it with an external battery back. Even though the company was purchasing the cables directly from Apple and then modifying it. Instead the company now offers a 'magic box' that splices into your existing MagSafe cable to work with their HyperJuice batteries (found here).
We recently took a trip out to NAB2012 and wanted to make sure we had enough mobile juice for our editor, and found that there was a cable available to work with our Tekkeon MP3450i battery packs that we have so many of. With all the Tekkeon batteries we have, this cable has been working perfectly and would provide us with many, many, many hours of run time for our MacBook Pro, MacBook Air, and of course USB power to all of our iPhones, iPads, and other camera accessories. I'm not sure if Apple is going to try and step in again and shut the operation down, but Tekkeon uses a 'recycled' modified cable to connect with select Tekkeon batteries. Hope some of you find this tip useful if you're looking to get some additional run time on your MagSafe powered MacBook Laptops.
Tekkeon MyPower All Battery for 600 / 900 LED Panels