This means you don’t have to own a Kindle Fire to watch Amazon Instant Video movies and TV shows on a tablet — or use Netflix or the iTunes Store to watch studio fare on an iPad. Amazon says that its new app enables iPad users to buy or rent more than 120,000 movies and TV episodes. They’ll have to make the transactions separately, though. (Remember that Apple collects about 30% from the transactions on its platform.) But people who pay $79 a year to become Amazon Prime members can access more than 20,000 titles without an additional charge. The new app will handle Amazon’s Whispersync, so people who stop a video in the middle on one device can turn to another device and pick up where they left off.