This can be made in to a keyring, necklace, earrings or anything else you can imagine. It is fairly simple, involving only 4 main steps to achieve the final product. It does require a 3D design package, but several are available free online and are very simple to install and use. If you don't own your own 3D printer then locating one is fairly easy, as most universities have 3D printers available for the public use and staff are normally more than happy to guide you through using it. If not, then there are other tech groups, for example Hacker Space groups, which have 3D printers they are happy for people to use and help you with your project.
Simply input the desired web address in to the QR generating website and then download the QR code it generates. Now is a good time to check that the code correctly redirects where you expect, so use your QR code reader on your phone to see if it redirects correctly.
Once you have uploaded the QR code image you need to draw around all of the black shapes in order to separate them from the background, to allow you to pull the background to a different depth, making it 3D. (the programs simply sees this image as a flat object, like a piece of paper or a photo, and won't recognize the shapes on it, so you need to outline each of the shapes so they can be pulled to a different depth)
Adjust the scale to give it the desired dimensions. Also, it is important to take in to considerations the size and accuracy of the 3D printer you will be using, as some custom built machines may have trouble with fine detail. Once you have adjusted the scale for height and width, pull up the background to the desired depth. (I went with 25mm square and 4mm deep).
If you know how to program and are familiar with Python then there is a script you can download and run that will outline the black and white images within the QR code and you can just scale it to the desired dimensions.
In order to convert the file you have created in to a format that the 3D printer can use it needs converting to G code and exporting (this tends to be the type of file 3D printers generally use, but their are other formats, so it might be worth checking what file type the 3D printer you plan to use accepts).
Insert the SD card in to the 3D printer and run the file. Make sure that the surface it is printing on to is clean and level, check that the distance of the nozzle from the plate is also correct, as the fine detail of the print might be dragged or damaged if the setting are not right. Allow the print to finish and the surface to cool before attempting to handle the print. At around 65 degrees Celsius the print will probably pop off the surface, but if not then a small tap from a chisel is normally sufficient. (For a print around 25mm square and 4mm deep it took roughly 90min to complete printing and used roughly 50cm of raw plastic).
Add contrast to the print by one of a variety of different methods, depending on what finish you want. You can simply colour the top surface in black with a permanent marker pen, or for a nicer finish you could infill the 3d sections with coloured latex or resin.
Use your QR code reader to check that the QR code redirects to the desired website. (QR codes tend to be pretty flexible and readers are able to still detect the desired site even if the code is not exactly correct, so you shouldn't have a problem getting the reader to recognize the code as long as there is sufficient contrast between the two colours you chose).
If you left a hole through the design then simply thread through the chain of a necklace, or you can use a small drill to produce a hole and then attach it using a small metal ring.
Enjoy your new necklace!