Burt claims his watch updates its time "by connecting directly to the cesium clock in Colorado via ultrasonic frequency." Later the graboids home in on him by the ultrasonic sound emitted by his watch. Firstly, radio controlled watches update their time by receiving signals, but they don't emit any signals - the battery would be way too weak for two-way communication. Secondly, they work on radio waves, not sonic waves. Thirdly, if a hypothetical time transmitter did work on ultrasonics, the smallest distance between Colorado and Nevada is some 435 km (around 270 mi). An ultrasonic signal strong enough to reach that far would probably be deadly within a sizable range around the transmitter.