Boundless has pitched its digital textbook service as the free alternative to expensive college textbooks, but the absence of mobile support and study aids has limited its appeal. The educational startup is addressing both of those issues today. To start, it has launched a native iPhone app that optimizes the web client's highlights, note-taking and summaries for a smaller screen. The company is also introducing a premium option for students who need a little motivation. Readers who pay $20 per textbook get access to a steady stream of flashcards and quizzes, with notifications to minimize any slacking. Diligent learners can grab both the app and premium upgrades today -- at least, so long as they have no qualms with Boundless' ongoing copyright disputes.