If I worked security at the Los Angeles Convention Center and saw someone walking in with that thing I'd probably detain them. ;-)
Actually as recently as 2004 I had a battery pack for a photographic flash that was a lot more cumbersome than that belt looks! I'd have killed for that thing!
That looks like a lighter weight version of belt packs that have been available for many years. If a guy had a TV camera on his shoulder he probably had a pack around his waist.