Getting current exchange rates with AS3

I am developing an AIR app for iOS and Android, it will need to know the latest exchange rates for a range of currencies each time it is used.

I have come across paid subscription currency information services from www.xignite.com and http://fxtrade.oanda.co.uk and also a service that appears to be free, from www.webservicex.net

Does anyone have any experience of these services, or know of any better ones. And can anyone suggest the best actionscript solution to access these webservice, e.g. REST, SOAP, or perhaps another way?