The Kno is a new twist on the tablet and e-reader concept, aimed at the college market; it allows students to view textbooks on two digital screens much as they would view them in their analog versions, with text, color images and graphics. The Kno was first shown in public last Wednesday at The Wall Street Journal's D8 technology conference in California. It is made by a company of the same name founded by Osman Rashid, who also founded Chegg, a Silicon Valley startup that allows students to rent textbooks. The device has two 14-inch screens, big enough to display two facing textbook pages without scrolling. It will also have a stylus to take notes with, a Web browser and support for Flash. It weighs about 5.5 pounds, and each slab of the tablet is a little thicker than half an inch. Compared with an iPad, the Kno feels large and heavy. But Rashid said to compare it instead with a 20-pound backpack containing textbooks, notebooks and a laptop. Rashid said the company had deals with several large publishers, including Pearson, McGraw-Hill Education, Cengage Learning and Wiley, to make its texts available. Kno plans to release a test version in the fall and begin selling it broadly before the end of the year. Pricing is unclear, but Rashid said it would cost less than $1,000. -- MIGUEL HELFT HELP IN FINDING THE MOST ECONOMICAL DATA PLAN Now that AT&T no longer offers a $30-a-month unlimited data plan, many smart phone owners may wonder how that affects them. For most, it's a chance to save money. But there is no need to guess. There are tools to help people determine their best plan. AT&T basically offers two plans, one allowing up to 200 megabytes of data for $15 a month and the other supplying two gigabytes of data for $25 a month. The trick to getting the best deal is to buy only as much as you use. And there are several ways to figure that out. One is with an app, AT&T myWireless, that shows data use. Or a user can dial (AST)DATA. ((AST)3282.) for a text message detailing a device's data use. Finally, users can check www.att.com/wireless. Six months of AT&T bills are available online, or you can look over your paper bills. If this is confusing or overwhelming, there are services to help, like billshrink.com and Validas.com, which can examine your bills and recommend a phone plan whether it's AT&T or not. -- ROY FURCHGOTT AFTER YOU ROCK OUT, THE GUITARS CAN BE STACKED Air guitarists can take one small step toward reality with PaperJamz, a set of musical instruments that look as if they have been run over by a steamroller. The toys, aimed at ages 5 and up, come from WowWee and will be available next month. The collection consists of six different decorated guitars ($25 each), a drum pad ($25) and a shoebox-size amp ($15). Each requires AAA batteries, and when seen from a side angle, is just a bit thicker than a slab of cardboard. Other than the on-off toggle switch, there are no real buttons or strings. Instead, children interact with a touch-sensitive surface that WowWee calls Active Graphics Technology. Children can strum along with up to three onboard songs, like 'Born to Be Wild,' or tap out the beat to 'Sweet Home Alabama' on the drum pad. Other than the strumming motion, there is no resemblance to a real guitar. The controls can be confusing, in part because the fret board doubles as a menu for selecting songs or modes of play. And the built-in speakers are feeble. But they can be significantly enhanced by plugging into the cardboard amp, just in case you have plans for a subway concert. -- WARREN BUCKLEITNER 