New Yorkers grumble about the daily wake-up call they get when the city’s garbage trucks arrive outside their windows. But it wasn’t just the noise that bothered Sam Saha. Sometimes, Saha says, the trucks would make all that racket even when there wasn’t much to pick up. The thought of all that inefficiency–the wasted fuel, time, and money–never left his mind. So he designed a solution. Saha–an inveterate tinkerer, IT guy, and software consultant–has created a sensor that tells you when a trash can is actually full. The idea is hardly the most glamorous extension of “the internet of things,” the sweeping effort to improve our lives through a new world of networked devices, from watches and glasses to thermostats and fire alarms. But Saha may be on to something truly useful. If trash collectors know when a can is full–and, more importantly, if they can identify the patterns that let them predict when cans get full–they can change their routes and schedules to pick up the trash only when they really need to.