Online reviews indicate how popular your favorite place is in general, but cannot tell you whether now is a good time to drop by or if you may be stuck in a crowd or waiting in line – this is where the Density Sensor comes into play.

No need to resort to complex spatial mapping or real-time video sensors with this gadget, a people-counting device that simply tracks passages through doors (attached to the frame). Some more obvious applications include specific bars, restaurants, coffee shops and other businesses that have time-of-day and day-of-week cycles to contend with, but the same data can also help you pick the DMV or grocery store with the shortest line.

In turn, businesses can choose what data to share with customers and what to keep for optimization purposes, offering discounts during less busy times or adjusting when to open and close. Compared to non-networked break-beam technology or real-time surveillance cameras, there is no need to wait for data or face privacy concerns.

Of course, up-to-the-minute incoming and outgoing traffic are just a starting point – architecture firms, for instance, could use extended datasets to anonymously track customer or employee flows through a building and use that data to optimize going forward, shaping extensions or remodels. Ultimately, one could imagine this system being replaced by more detailed heat-mapped trackers keeping tabs on entire spaces, but for now this is a cheap solution to a long-standing problem.