Terms of the deal were not disclosed.
Today, Ivona's technology powers the text-to-speech, "voice guide", and "explore by touch" features on Amazon's tablets; with this acquisition, expect deeper integration.
Audio-based input has become a hot commodity in recent years, as technology's biggest companies explore non-visual ways for users to manipulate mobile devices. Apple's Siri is the most prominent and consumer-facing of the bunch, but the technology also powers in-car telematics systems (such as Ford's Sync) and enterprise functions (such as transcribing physicians' notes about patient visits).
If you're interested, I wrote a lengthy feature about the subject at ZDNet's innovation-minded sister-site SmartPlanet.
Amazon bringing Ivona (and its 17 languages) into the fold mirrors the trend of technology companies adding specialists to their vertical stack. It's no longer enough to simply manufacture a tablet; today, you must control the components, algorithms, and software ecosystems, too.
The biggest value of acquiring a company like this isn't just the enabling technology, but the tremendous amount of data it has on hand as it's refined that technology. In many ways, we're seeing an escalating war on the back-end between tech's biggest players: Apple (via Nuance), Google, Microsoft, and now Amazon.
Ivona also sells its wares to companies interested in applications for accessibility, public announcement/transportation, telecommunications and e-learning; it's unclear where those deals will stand after the acquisition. (Most likely, they'll be left alone, unless they directly compete with Amazon's products.) And the sky is the limit for Ivona's technology to be incorporated in Amazon's enterprise businesses.