The modular components that could be added or replaced to the wristband include batteries, haptic devices that provide a sensation to the user, displays, photovoltaic cells, cameras, GPS sensors, speakers, as well as a range of health sensors including thermometers, hygrometers, blood pressure sensors and sweat sensors.
These modules to track body changes are perhaps the most interesting idea as Apple chief executive Tim Cook has expressed an ambition to get into the health space. Last year, Cook touted health care is an "enormous" opportunity for Apple and the Watch would play a key part.
"One day, this is my prediction, we will look back and we will wonder: how can I ever have gone without the Watch? Because the holy grail of the watch is being able to monitor more and more of what's going on in the body. It's not technologically possible to do it today to the extent that we can imagine, but it will be," Cook said at the Startup Fest Europe event in Amsterdam.
One of the modules could also be a "cellular antenna", potentially laying the groundwork for an Apple Watch that can give extra functionality without being tethered to an iPhone. Currently, an Apple Watch needs to be wirelessly connected to the handset to carry out functions that require cellular connectivity. But if there is a cellular antenna built in, this could allow a user to make calls or send texts without connecting to an iPhone.
Apple was not available for comment when contacted by CNBC.
It's important to note that Apple applies for, and is awarded many patents, a large number of which don't see the light of day in terms of becoming a real product.
Apple does not release official sales figures for the Apple Watch. Nevertheless. In early December, Cook said in an email to Reuters that the Apple Watch was on for its best quarter ever in terms of sales. Independent analysis from IDC showed Apple Watch shipments fell 71 percent year-on-year in the third quarter of 2016 to 1.1 million units.