Sprint shot back at T-Mobile's recent "7 night stand" test-drive program with a 30-day free trial of its own, announced Monday at a press event in Chicago.

That'll give customers a chance to kick the tires on Sprint's newly announced nationwide HD Voice service, expanded 4G LTE network, and even its exclusive handset, the Samsung Galaxy S5 Sport, a rugged, health-focused version of Samsung's flagship phone, coming to Sprint next month.

Exclusive Galaxy S5 Sport launches July 25

While Sprint led off its Monday event in Chicago with various network upgrades, CEO Dan Hesse quickly segued into debuting an exclusive device to take advantage of them: the Samsung Galaxy S5 Sport. Available on July 25 in Electric Blue and Cherry Red, the Galaxy S5 Sport appears to be a variant of the Galaxy S5 Active, with a rugged, textured body and the same 5.1-inch Super AMOLED display, 2GB of RAM, and 16GB of internal storage. It will support the Spark network on Sprint.

Although very similar to the Active in hardware (including an IP67 rating for water- and dust-resistance), the Galaxy S5 Sport will have an exclusive package of fitness apps and tools in collaboration with Under Armour and its MapMyFitness team. Naturally, it will also sport Samsung's S Health app, which collects health details including heart rate data from the S5 Sport's built-in tracker. The Galaxy S5 Sport is also IP67 water and dust resistant

Under Armour CEO and founder Kevin Plank helped introduce the accompanying Sprint Fit Live app, which includes built-in MapMyFitness functionality and allows users to do everything from measure real-time workout progress to access Spotify playlists. It will launch with 12 free months of the premium MapMyFitness MVP service.

And to get prospective new Samsung Galaxy S5 Sport buyers focused on its various fitness capabilities, Sprint will offer $50 off of the price of an accompanying Samsung Gear Fit tracker, as well as 50 percent off the price of select fitness earbuds or JBL headphones.

Clearer calls and expanded 4G LTE coverage

While the new phone stole the show, Hesse also announced a slate of network improvements, including a nationwide expansion for Sprint's HD Voice service. HD Voice expands the number of transmitted octaves from four to seven, delivering clearer, fuller-sounding voice and audio on supported handsets--Hesse described the enhancement as "the greatest improvement in the history of wireless voice." More than 60 handsets currently support the feature, including the Samsung Galaxy S5 and iPhone 5s, and Sprint says that some 16 million of its customers own devices that can take advantage of the upgrade today.

Sprint is also expanding its 4G LTE service to 28 new markets, which brings the grand total to 471 cities--with plans to cover 250 million people by mid-year. Meanwhile, Sprint's Spark LTE service, which offers even speedier data use via combined 1.9GHz and 800MHz spectrums, has expanded into St. Louis, as well as Winston-Salem and Greensboro, North Carolina, bringing its grand total to 27 cities. Spark will begin utilizing 8T8R radios for even faster data transmission starting this summer.

Sprint is so confident in its enhanced network--which it's billing as America's Newest Network after significant hardware enhancements--that it will launch a 30-day guarantee program this Friday, June 27 that allows any customer to return a handset purchased and activated on a new line of service to receive his or her full money back, including any service and activation fees paid. Sprint marked the announcement with a montage of Denzel Washington making guarantees in several hit films; no real appearance from Washington, though, sadly.

Sprint also used the occasion to announce a new expansion of its Framily Plan service: the Framily Wall, a secure space for all members of a particular plan to share messages, photos, video, and audio amongst each other. The Framily Wall will be available free to all plan members soon, while a premium version (at a cost of $3 per month) will expand the amount of cloud storage available and allow users to upload and store videos and other media.