Convert Any Unit Free
If you seek a single app for converting currency, measurements, temperatures and other stuff, try Convert Any Unit Free. The app performs unit conversion quickly, thanks to its autocomplete feature. You type the first letter of the unit, and the app does the rest. There's a bookmark feature for saving frequently used conversions, too. The ads, which perpetually loiter at the bottom of the screen, are a bit annoying, but the app is free and optimized for iPhone, iPod touch and iPad. Though the similar The Converted app ($3) hasn't been updated since the fall of 2013 (as of this writing), it's a good option for those traveling overseas because it doesn't need a data connection to work its magic.