Wal-Mart will begin offering a branded cell phone service next week, offering no-contract, unlimited voice and text service for $45 a month. The service will use T-Mobile's network, but phones purchased from Wal-Mart will not be transferable to a T-Mobile branded calling plan.

Of note for content publishers eyeing Wal-Mart's massive customer base as a potential new mobile audience: Only one of the five phones currently being offered is a smart phone (the Android-based Motorola Cliq XT). And while voice and text plans are priced at a discount, data is not -- though that comes with a twist.

According to Engadget's Darren Murph, each plan includes a one-time 100MB data allotment; after that consumers must purchase one of three "WebPak" add-ons: "$10 buys you an extra 200MB, $25 gets you 500MB and $40 gets you 1GB." In contrast, 2GB of data from AT&T costs $25.

However, in contrast to AT&T, Verizon and others, Wal-Mart's data allowances do not expire each month and are shared by all phones with the same account. So a family of light data users may be able to purchase the $40 plan and expect it to last several months, as opposed to paying another carrier $25 to $30 every month for each phone, regardless of how much data they actually consume.