Accurate measurement underlies a huge amount of modern technology. Atomic clocks, fiber optical communications systems, and many other types of hardware require accurate and precise measurements. The laws of quantum mechanics, on the other hand, are designed to annoy anyone obsessed with precision. In some cases, it's impossible to increase precision—not because the laws of physics prohibit knowledge but because the probe with which we measure is limited by quantum mechanics.
This limit is often referred to as the standard quantum limit. However, you can, with a great deal of pain, prepare special probes that beat the standard quantum limit. In this case, a different limit applies, called the Heisenberg limit.
You can't beat the Heisenberg limit. So the big question is "can we find a method that reduces the amount of pain required to approach it?" The answer, it seems, is yes.