Fan Zheng runs Happy Child, a late night snack bar serving cocktails and cheeseburgers in Toronto, and one of the businesses in the city using a new, high-tech marketing tool.

It's basically a sensor, designed by a tech company called Turnstyle Solutions, that collects location data from customers' smartphones. The sensors can easily pick up data from phones connected to the snack bar's WiFi netowrk. Creepy? Maybe. But Zheng says he's not spying on customers.

"I wouldn't say that. The information that we get is aggregated data. So it's not as though as soon as a customer walks in we have access to their Facebook and we're snooping on their profiles. It's more like statisical profiles analytics that we get. It's very general," he says.

Zheng says the customer reports inspired a simple marketing idea. A recent report about his customers' other check-ins showed that many of them frequently go to the gym. So he had some workout tank-tops made that featured his restaurant's logo and gave them out to his customers to spread the word at the gym. He says it helped bring in new customers who might otherwise not have heard about his drinks and hamburgers.

Zheng, though, admits his customers don't know about his technology, though he bristles when asked if his customers know they're being tracked? "My customers aren't being tracked," he says. "They have the option of turning off their WiFi signal. If you go anywhere and if you're using someone's WiFi signal, you're being tracked. It's common knowledge."

Zhang says he's not out to invade anyone's privacy, and isn't able to use the information he receives for a personal advantage.

He says the sensors are placed near the door and can pick up smartphone data from customers as well as passersby. Most of the participating businesses, including cafes, yoga clubs and restaurants, in Toronto don't disclose to customers that this marketing tool is in use.

"I think because this technology is so new, and this topic hasn't really been debated in the mainstream media until now — and I'm glad the conversation is being had now — but I don't feel as though I am necessarily being invasive in terms of people's privacy," he says. "I'm not going into their Facebooks, I'm not analyzing their habts on a personal level. It's a very generalized overview."