Tracking people via their cell phone battery usage

BBC : Most people know that their phone can be tracked through its GPS, cellular, or Wi-Fi connectivity. That’s why phone applications require the user’s permission to access those services. However, no permission is needed to read the phone’s power consumption, and that information, according to a new study , can also be used to infer a user’s location. The amount of power a phone uses depends on how far it is from a cell phone tower and how many obstacles, such as trees or buildings, are in between. Although phones run many applications simultaneously that also drain the battery, that noise is not correlated with the phone’s location and can be ruled out by a machine learning algorithm. The researchers say that if one knows the general area in which a given user moves, the application can learn information about the user’s location in just a few minutes.