Bitcoin. Don’t leave home without it.
Crypto-currency is more than just a speculative commodity. In many parts of the world it is being used to buy and sell things - just like real money.
During a break in Argentina over the new year, I discovered to my great surprise that Bitcoin is a practical and relatively cheap way for an Australian traveller to exchange cash while avoiding heavy charges.
At least it is in Argentina, which is somewhat challenged, to put it mildly, …