Yahoo’s relaunched its flagship purchase, Summly, for iPhone and iPod touch devices this morning. The app uses artificial intelligence and natural language processing algorithms to deliver short summaries beneath story headlines. The new features are prominently on display in the “Visual” mode, wherein headlines and summaries are overlaid atop blown-up thumbnail backgrounds. You can now also specify your section and topic preferences, making your Yahoo news experience more personalized. Yahoo also gave the app a major upgrade to its video and image searches. This is another big app release for Yahoo, who also released Weather and Mail apps last week, and demonstrates their continued effort to penetrate the mobile app market.