Sometimes, a person’s biggest worry can simply be whether or not they’re getting a good night’s sleep. So it makes sense that sleep trackers have become such a popular and well-received technology.

The basic premise of a sleep tracker is straightforward. The device typically offers users two main pieces of information: how long they’ve slept and what the quality of their sleep was. These conclusions are reached by collecting various kinds of physical data during sleep, and through this information users can adjust their sleep schedules or sleep habits accordingly, leading to a healthier sleeping experience.

But tracking sleep is notoriously difficult; after all, most trackers are worn around your wrists or midsection, and not the brain–which is where all sleep activity occurs.

When it comes to tracking sleep, scientific sleep studies are considered the most accurate method. Participants in these studies are attached to wires that monitor brain waves, rapid eye movements, oxygen levels, breathing patterns, heart rate and more. One study can produce over 1,000 pages of data, and it’s no surprise that the direct analysis of brain activity by professionals is the definitive way to monitor sleep. But it is expensive and a hassle, while wearable or bedside sleep devices offer a convenient and affordable way to track sleep.

Since sleep trackers cannot monitor brain waves, improvements are focused on other data that is possible for the devices to record. The best sleep trackers are able to record much of the same data that sleep studies do, primarily tracking heart rate and breathing patterns to determine sleep behavior, and some sleep trackers can also provide environmental data including light levels, sound and temperature. Even further, trackers can prompt users to answer lifestyle questions that might affect sleep such as diet, stress, alcohol consumption and so on. Evidently, there are a multitude of ways that trackers can record sleep data, but the question then remains: If sleep studies are the most accurate form of sleep measurement, how close do sleep trackers come through their compensating methods?

The reality is that until sleep trackers are able to monitor brain waves, they will remain, as experts say, more of a guesstimate than an accurate measurement of sleep. However, this doesn’t mean that sleep trackers are useless. Sleep trackers still provide plenty of insight based on the other data it collects.

The main reason for performing a sleep study is usually to diagnosis sleep disorders, such as sleep apnea. If a person is worried that they might have a serious sleep disorder, this is likely the best route to go. But for the rest who are just looking for ways to improve their sleep, the information and guidance offered by sleep trackers is more than enough to do so. In addition, the act of tracking increases mindfulness, which encourages people to make better sleep choices.

As technology evolves, it becomes able to perform more complex tasks with less effort. It’s not far-fetched to say that with time, sleep trackers could realistically become as accurate as sleep studies, giving consumers full control over their sleep.