I always wondered why we didn't put up a chain of tethered radar blimps along the Main Supply Route from Kuwait to Baghdad. I remember seeing these deployed in the Florida Keys to catch drug traffickers. 24/7 surveillence of the MSR at very low cost. It's gotta be cheaper & better coverage than flying UAV's.
They've deployed some since at least 2005 (more detail here) and have plans to possibly deploy many more with much more capability.