In my paranormal romance novels set in 2096 Chicago, I 'invented' cell cards. Basically a techie gadget unique to a person that you could use on any computer or public 'phone'.
Based on the current technology, it's not a completely new idea. There are all kinds of variations on the market even now and we get closer to that type of device with every generation of technological improvement. Just the amount of data stored in that stripe on the back of your credit or debit card - even your hotel