I have used a CGM for years now, but I don't know all of the models - only a few of them. In my experience most of the time the manufacturer offers some kind of cloud service to store your data (given your cousin is using a device that is capable of transmitting said data) and there are free to use services like Glooko (it's the one I use - there are others) you can connect different devices to store and visualize these data. It helps a lot exploring patterns and finding ways to improve my therapy.