I’ve never used one. I’m googling it but thought i’d also ask here. I’m in US, other person in UK. Can they go get a card, read me off the number or whatever and let me give them a couple hundred dollars instantly?
It will depend on the T&C’s of the card issuer. Some of them can be topped up by SMS or a simple bank transfer. The cardholder should call their issuer and ask. Note that there will certainly be a fee.
If the amount is small, it might be simpler to put a few Dollars into an envelope and post it. The cardholder can then go to one of the many currency exchanges and get GBPs
One thing to take into consideration is that the US is not in the Single Euro Payments Area (the UK is), so it may not be straightforward to make a fee-free transfer. Otherwise it’s true that there are cards one can buy at a bank or post office that can be activated online, have an IBAN printed on the back to transfer money to (up to some limit of a few thousands), and can be used to withdraw cash from ATMs and to buy stuff online or in stores. Make sure to check the T&C carefully first, as bob++ advises.