Amazon Kindle for Android App Updated has introduced new features for its Kindle for Android app, including the ability to search within an e-book via typing or voice. Kindle's competitors include the Nook and Apple iPad. has added new features to its Kindle for Android app, emphasizing yet again the online retailer's strategy of building out its e-reader software in addition to its Kindle e-reader device. The company finds itself locked in competition with not only other e-reader manufacturers such as Barnes & Noble, which markets the Nook, but also Apple's iPad.

Kindle for Android's new features include the ability to search within an e-book via typing or voice; add notes and highlights to text, and have those notations sync between devices; and look up terms in Wikipedia.

Users can also lock their screen in landscape or portrait mode, and view additional details about an e-book through social-networking site Shelfari. The free Kindle app is downloadable through Google's Android Marketplace.

Amazon's update comes as the company prepares its holiday marketing push for the Kindle. The first 30-second spot of the Kindle's new television ad campaign features a bikini-clad woman extolling the virtues of the e-reader-notably its $139 price-point-while the man beside her struggles to read his tablet PC's screen in bright sunlight.

The WiFi-only version of the Kindle retails for $139, while the next-generation version with 3G connectivity sells for $189. Amazon's latest updates to the device include a higher-contrast e-ink screen, longer battery life, Wikipedia access, support for password-protected PDFs and a more lightweight body.

Analytics firm In-Stat predicts that e-reader shipments will grow from around 12 million units in 2010 to 35 million in 2014.

"Tablet PC shipments are taking off, fueled in particular by the Apple iPad introduction. Yet, there will still be a revenue opportunity for e-reader suppliers and OEMs since tablet PCs and e-readers target different consumers," Stephanie Ethier, an analyst with In-Stat, wrote in a Sept. 14 research note. "Standalone e-readers will address the needs of avid readers, to whom the reading experience is central. Tablets are better suited for consumers who prefer a stronger multimedia experience, and only light reading."

While much of Amazon's marketing muscle seems devoted to promoting the Kindle device, it also seems determined to spread Kindle software onto as many platforms as possible. In addition to Android, the company markets Kindle apps for Windows PC, Mac, BlackBerry, iPhone and iPad. That conceivably allows Amazon to sell e-books even to those who don't own a Kindle; and given that the Kindle's recent price drops doubtlessly means less financial return for Amazon on hardware, e-book sales may represent the company's key profit opportunity.