The list of things with which you can pay for a sandwich is getting smaller all the time. Phones, fingers, eyeballs… Even actual coins. Ahem.
In fact it's increasingly simpler to list what you can't use than what you can.
Now a new concept by Swedish startup Quixter has an even simpler solution. They want you to use your veins.
The team say that since no human has the same pattern of veins under their hands - it's just like a fingerprint - it could be easier to use this to authorise payments than a password or credit card.
They've set up 15 of their machines around the campus of Lund University and are now testing it to see if the fast payment system takes off.
Founder Fredick Leifland said:
"I got the idea when I was in line at the supermarket and I saw how complex a process paying is. It takes a lot of time so I thought there must be an easier and quicker way to pay and that was the start of Quixter."