I think it's a real shame that the iPhone doesn't have an Exchange Rate widget. Perhaps someday there will be, now that Apple is opening up the platform. In the meantime, I looked for a Exchange Rate web-app for the iPhone at the Apple site. I could only find one, which isn't too bad, but I was hoping for something with charts, etc., a la the Stock widget.
Then it struck me: since the Stock widget is getting its feeds from Yahoo!, I should be able to use their special codes for the FX market. Voila ! Here are the ones I use:
* GBPUSD=X $US / £UK * GBPEUR=X €EU / £UK * EURUSD=X [...]