how would you A/B test iPhone apps?
wmeredith: Design an iPhone app that's a CMS pulling in data streams (XML) and displaying them to users. Set the first queried data stream to be the A/B switch and all other data is pulled into the app dependent on the state of that switch. This is all assuming you're talking about testing within the app itself after it has been downloaded.
(I'm an SEM/SEO UX guy, so this is out of my league, but I think that makes sense.)