The US Army has recently become interested in long term battlefield surveillance. One of the results of this is a blimp called LEMV (Long Endurance Multi-Intelligence Vehicle).
The rise of modern terrorism, sharply increasing costs to recruit and equip professional soldiers, and issues of energy security, are forcing 2 imperatives on modern armies. Modern militaries need to be able to watch wide areas for very long periods of time. Not just minutes, or even hours any more, but days if necessary. The second imperative, beyond the need for that persistent, unblinking stare up high in the air, is the need to field aerial platforms whose operating costs won’t bankrupt the budget.
Video from New Jersey test flight Aug 8th, 2012: