This is a valid point personally it would be good for the app to have a secondary or third location to pull the currency conversation data incase your main site goes down, so the user seamlessy keeps working on that 2nd/3rd site and you can release an update to fix it (which there would be no real rush since the user is happily working). Also i agree with the converstions for other measurements, if you built in a whole load of standard converstions like the iphone app "converter" you would have a very powerful all-in-one app. Great work !!