Wireless plans: Is Wal-Mart's new family plan for you?

Wal-Mart announced Monday a new twist on its inexpensive, no-contract wireless plans: a low-cost family plan with unlimited calling and texting.

Called Walmart Family Mobile, it charge only $45 a month for the first line and $25 a month for each additional line. Best of all, users aren't locked into a contract and they don't have to prepay.

The plan, which runs on the T-Mobile network, will be offered beginning Sept. 20. But call ahead before visiting your local Wal-Mart store, since not all stores will be offering the deal.

For families wanting unlimited cellphone and texting service, the plan costs less than competing plans from big carriers. Verizon, for example, charges a little over twice as much for similar service. Wal-Mart claims it can save a family of three $1,200 a year versus either Verizon or AT&T.

But smartphone users who are heavy users of e-mail or the Web should weigh other possibilities.

Under the Wal-Mart plan, each cellphone comes with an allowance of 100 megabytes of Internet service. That's not 100 MB per month. That's 100 MB total.

After they use that up, users have to buy extra allotments of data, starting at $10 for 200 MB. For people accessing large chunks of mobile data, the charges can add up quickly. Data plans from other carriers could prove cheaper over time.