The big news Sony’s press conference for its new line of eReaders was the deal with AT&T (NYSE: T) to provide its 3G wireless connection to the Daily Edition, Sony’s first wireless reader. Neither Sony (NYSE: SNE) nor AT&T would say what the revenue split is. But it’s probably not too different from the arrangement between Sprint (NYSE: S) and Amazon (NSDQ: AMZN), for the Whispernet wireless 3G system that lets Kindle users download books, blogs, newspapers and magazines. And if the Sony/AT&T exclusivity agreement is like its rivals, the revenues aren’t going to add up to much.

—Best guess: Sprint told investors last May that Kindle drove most of the wireless carrier’s 394,000 new wholesale subscribers. Around that time, we focused on a best of what sort of revenues Sprint was getting, citing a blog post from Roger Entner, SVP, Nielsen’s Head of Research and Insights for Telecom, who estimated the average revenue per Kindle user was a meager $2 a month. That made our Tricia Duryee wonder whether Kindle-like devices could become a healthy new subscription model for Sprint, considering that direct postpaid Sprint subscriber has an ARPU of $56 a month.

In any case, Sony isn’t the only wireless eBooks device AT&T is powering. In July, AT&T said it would be handling the connection for Plastic Logic’s e-reader. So altogether, assuming eBooks really do start taking off, this could eventually become a meaningful business for AT&T, especially as the eBooks wars are really heating up.

• Sony Unveils Three Would-Be Kindle Killers—Pocket, Touch and Now, 3G Wireless With AT&T
• Barnes & Noble Teams Up With AT&T For Free WiFi
• AT&T To Provide Data Connectivity For Plastic Logic’s E-Reader; More AT&T Network Overload