WWDC is right around the corner, which likely means San Francisco will soon be seeing a sudden influx of international tech enthusiasts. Many of them will be buying drinks for one another, and they might want to keep track of exactly how much money they're losing spending back home. Instead of doing mental calculations on the spot, they should use the Currency app made by Simple Simple.

It can keep track of your favorite currencies (of which there are over 160 to choose from) and list them together with a primary currency pinned to the top of the list. Tap on the primary currency, enter a number, and each currency on the list will display the conversion for that amount. Swipe right on the primary currency to reset it back to 0, or swipe left on it to display the previous amount you entered.

The app is simple, well-designed, and easy on the eyes. It only costs a buck too, so check it out.