When Apple delivered the first long-awaited smartwatch to its customers on Friday, a small factory in Shenzhen, Guangdong province, had already sold tens of thousands of Apple Watch look-alikes worldwide for a fraction of the price.

Zheng Yi, founder of smartwatch factory YQT Electronic Technology, is expecting "explosive demand growth" this year because of the Apple Watch release.

"Apple ignited customers' craze for wearable devices. We will definitely benefit from it," he said, sipping a cup of tea at his office close to the Shenzhen airport.