This was a lifesaver - I've been stuck in a foreign country carrying around two phones for the past four months.
Saved me when I was in Vietnam.
And they aren't illegal -- many first world countries require that phone companies unlock your phone if you request it, and of those that don't, I don't know of any where the hardware is illegal. They are openly sold in stores in the USA, which I think is one of the most restrictive countries about such things. Calling emergency services for non-emergency purposes is not usually legal, but that doesn't seem to be what you are saying.