New tablet splits difference between smartphones, laptops.

Today Apple CEO Steve Jobs unveiled the iPad, the company's hotly rumored tablet device.

When the iPad begins shipping at the end of March, it will come in three sizes: A 16GB model for $499, a 32GB for $599, and a 64GB for $699. You'll be able to add 3G connectivity to each of them for $130 more.

 The iPad looks like a supersized iPhone. It's a half-inch thick, weighs 1.5 pounds, and has a 9.7-inch LCD screen (with 1024 by 768 resolution). It will use a custom-made 1GHz CPU and flash storage and, Jobs claimed, will get up to 10 hours of battery life.

For connectivity, in addition to the optional 3G, it has 802.11n, WiFi, and Bluetooth 2.1; it syncs to a Mac via USB. To feed those 3G connections, Jobs also announced two new cellular data plans from AT&T: $14.99 a month for 250MB of data, $29.99 a month for unlimited data; both are prepaid, neither requires a contract.

In addition to demoing the iPad's calendar, Web, and e-mail clients, Jobs also introduced a new app, called iBooks, which will manage e-books on the iPad. While crediting Amazon for its pioneering efforts with the Kindle, he announced that Apple was opening its own e-book store for the iPad. He said that Penguin, Harper-Collins, Hachette, Simon & Schuster, and other publishers were already signed up to supply titles. Those titles will use the ePub format—an open e-book standard.

Tthe iPad will also run third-party software. Senior Vice President Scott Forstall said that the tablet will run most existing iPhone apps unmodified, right out of the box. Those apps can run at their existing size in a black box or can be doubled to run in full-screen mode. Apple is also making a software development kit available to developers, to help create apps specifically for the new device. To demonstrate what vendors could do with those tools, Forstall introduced representatives from Gameloft, Electronic Arts, the New York Times, and MLB.com to show off iPad apps they'd already built.