I want to be able to withdraw cash from atms outside the US.
Or Wirex, they're coming to the US:
Wirex has extra fees (on top of ATM/bank fee) and low daily limits for ATM withdrawals and may not be too attractive for that purpose (Wirex is more fit for paying with the card in store).
Although if they get more (and more, and more) customers maybe they'll reduce those fees, but .. that's just a hope.