2003 Ford Taurus giant cricket under my hood

Please listen to this noise....
http://www.youtube.com/watch?v=OuLcG8YBzzU

It really seems to be coming from the opposite side of the engine, away from the belts & pulleys (hard to tell from the video). And, the water pump, alternator, idler pulley, and belt have all been replaced within the last 1 1/2 years. Although, there is a slow nuisance leak from the lower radiator hose that I suppose could have been blowing coolant around and prematurely corroded something? It's also been leaking oil for a while now (I do keep it topped off). I'll have to take the belt off tonight after work and see if i can feel any bearing wear (maybe fire it up for a second without the belt turning anything?)... If it is just a squeaky bearing on an accessory I can fix that...replaced plenty of that stuff in my day...i'm just worried that it's coming from inside the engine...seems like a little different sound than I usually hear when a bearing goes out...too rhythmic? Does this car have hydraulic lifters...can a rocker arm assembly make this kind of noise? 3.0L Vulcan engine.