In "No Country for Old Men," Llewelyn has a satchel containing money, and a lot of people are looking for it. Helpfully, from their point of view, the satchel also contains an electronic device that emits a signal, facilitating electronic tracking. Llewelyn is unaware that the device is in the satchel.
In one scene in the film, we see Chigur driving around with an electronic tracker on the seat beside him. As he passes a motel, the device begins beeping, indicating that he's brought it close to the satchel. The tracking device seems to work like a Geiger counter, beeping faster as it comes closer to the signal-emitter but only when within a couple of hundred feet.
It’s hard to imagine how this allowed him to find the satchel. Was Chigur just randomly driving around the state of Texas, hoping to come within this short distance of the prize? It strikes me as a nonsensical plot element that the emitter should be packed into the satchel of cash at all, if it could only serve as a sort of hot-and-cold game for players already within a few hundred feet of the satchel.
How did this electronic tracking system help in the search for the satchel of cash?
PS As @magarnicle (sort of) pointed out in a note, Chigur had other information that helped him find the satchel. But I meant to ask how the tracking system was supposed to work, why the idea makes sense. If Llewelyn had chosen to take the satchel to a town that was not listed on his phone bill, would the tracking system have been helpful?