From today through Sept. 4, customers who buy the new Samsung Galaxy S III or other 4G Samsung Android devices can pick from one of three second devices free. The offer also applies to Samsung's Galaxy Tab 10.1, while supplies last (the tablet has been banned by a California judge in an Apple patents suit, but current inventory may be sold).

Back to School Promotion

The three free devices are the Samsung Galaxy S II (regularly $149), Samsung Galaxy S Blaze 4G (regularly $99) and the Samsung Galaxy Exhibit 4G (regularly just $29.99). New and existing customers will get a mail-in rebate card after signing up for a new two-year contract on the unlimited Classic plan or for a zero-cash down payment after a mail-in Visa rebate gift card when signing up on a new Unlimited Value plan.

If you don't need two phones, the older Galaxy S 4G is available for free on its own with a two-year plan.

The buy-one-get-one deal is part of an early back-to-school promotion that T-Mobile hopes will entice new adopters or plan-switchers to grab up premium devices to stay in touch in the fall.

"As we approach this busy season for families, we know it's important for them to easily and affordably stay connected, which is why we're making it simple to step up to 4G on our most popular Samsung Galaxy devices," said Andrew Sherrard, senior vice president of marketing, T-Mobile USA, in a statement.

Top of the Heap

Samsung is the leading mobile -phone manufacturer in the world, according to first-quarter data , after having knocked Nokia off its longheld pedestal. According to Strategy Analytics, South-Korea-based Samsung controlled 25.4 percent of the market, compared with Nokia's 22.5 percent. Apple's single offering, the iPhone, amounts to 9 percent.

"At this point, the Galaxy S III is considered one of the choicest Android phones available, so that could generate lots of interest and -- potentially -- a significant number of new subscribers" for T-Mobile, said Charles King, principal analyst at Pund-IT. "Plus the sale could also tip smartphone fence-sitters toward signing up for service plans."

But, he told us, the sale "probably won't pique the interest of consumers on the hunt for the next new thing" -- which typically becomes available in time for holiday shopping.

While it is still trailing the other three big carriers and has recently had a leadership shakeup, King said, "T-Mobile seems intent on being a serious mobile player.

"The $4 billion breakup fee paid by AT&T for the failed merger should provide some breathing room, and the recent spectrum swap with Verizon could help the company do better in core urban markets."