I've been developing an iOS application, and I've confirmed that it works fine on the iPhone 4. I have never tested it in a 4th generation iPod touch.
Recently I distributed the app to several testers (using a service called TestFlight). Only two of them are having problems downloading/installing, and they happen to be 4th generation iPod touch users.
So this leads me to my question - will an app that can run on the iPhone 4 be able to do so on a 4th generation iPod touch? Maybe their devices can't download/install the app because they actually can't run it.
The question at http://store.apple.com/us/question/answers/ipod/will-all-the-iphone-apps-work-on-an-ipod-touch/QTH2T4XUYF29DAUUA says
Most apps will work on the iphone and the ipod touch but some apps will require things that only the ipad or iphone has.
What are those specific things that an iPhone 4 may have that are lacking on a 4th generation iPod touch?
The app doesn't really do anything fancy. It uses Game Center, it has In-App purchase, an accelerometer... All of that seems to be supported by the iPod touch.