I just bought an iPad and will get an iPhone in July. When I look at the App Store I see that an application has different versions whether it is to be used on an iPad or an iPhone. For instance, GoodReader has a different app for the iPhone and the iPad. If I buy the iPad app, will I be able to install it on my iPhone when I get it in July or will I have to pay again to install it on my iPhone? Out of curiosity, could you tell me if it is possible to use an iPhone app on an iPod Touch?