Creating a USD charge on a GBP account:
$ curl https://api.stripe.com/v1/charges \
-u REDACTED: \
-d amount=400 \
-d currency=usd \
-d card[number]=4242424242424242 \
-d card[exp_month]=04 \
-d card[exp_year]=16 \
-d card[cvv]=390 \