You have a: BlackBerry
Try: WorldMate Live. It's available to BlackBerry users at the newly launched BlackBerry App World. The easiest way to get WorldMate Live is to search for it at App World from your phone (App World can take up to 10 minutes to download to your phone; your BlackBerry needs a trackball and software version 4.2 or higher to operate it). After downloading App World, it takes about three minutes to install WorldMate Live.
Bonus: Besides coverage of 160 currencies, the download also provides weather reports, itinerary organizers, and comparison charts for international clothing sizes.
You have an: iPhone
Try: ACTCurrency, which has more than 190 exchange rates available and updates when you hit the refresh button. Install it on a phone via the iTunes App Store (search on "currency" to find it). It took our tester about three minutes to download.
Cost: $1. There is a free version of ACTCurrency that only converts dollars and euros, but we found the $1 version to be more useful because of the multiple currencies. There are other free currency apps out there, but we found ACTCurrency far more convenient than the others, which have no manual update buttons and don't update automatically often enough.
Bonus: You don't need to press an enter button to get results because the tool converts as you type.
You have a: T-Mobile G1 phone
Try: aCurrency, which takes less than a minute to install and covers over 160 currencies at last count. The easiest way to download it is straight to your phone from the Android Market, which is similar to the iTunes App Store—you'll find the app by searching for "currency" and then looking for aCurrency.
Bonus: Every time you open the app, it automatically updates rates by accessing the Internetyou don't have to remember to update it yourself.
You have a: Samsung Blackjack, Motorola Q, or other PDA with standard Windows Mobile software
Try: WorldMate Live, which has features similar to the version for BlackBerry (above). Go to worldmate.com, and choose to receive this app on your phone via a link in a text message or e-mail (not an attachment). It takes up to 10 minutes to download. The application works on the devices listed here.
Bear in mind that if you're traveling somewhere that lacks Internet access, each app will base its calculations on the data that it most recently downloaded, giving you a fair approximation of prices. For up-to-the-minute info, you must activate an app while your device has a Internet connection.