RadioShack and T-Mobile USA announced that beginning today, the new Android-based T-Mobile myTouch 3G, as well as an assortment of T-Mobile products and services, are available in more than 4,000 RadioShack stores across the United States and Puerto Rico.

The myTouch 3G joins additional T-Mobile postpaid devices available from RadioShack, including the BlackBerry Curve 8900, the Samsung T239, the Samsung Comeback, the Samsung Gravity 2, the Samsung Behold and the Sony Ericsson TM506.

The announcement brings to fruition a retail partnership that the two companies agreed to back in July. By offering its service and devices through RadioShack, T-Mobile expands its retail reach, while RadioShack continues to diversify its portfolio of wireless service providers. In addition to T-Mobile, Radioshack is now a certified reseller of service and phones from AT&T, Sprint and Alltel Wireless. 

The move comes at a time when selling smartphones is proving profitable. According to recent reports by ABI Research and NPD Group, smartphone sales are on the rise, bucking a continuing trend toward declining mobile phone sales overall.

The NPD Group found that while sales of new smartphones reached only 28 percent of overall consumer purchases (feature phones account for 72 percent of the total market), smartphones still enjoyed a 47 percent increase in the category’s share since last year.

Meanwhile, ABI Research reported that second-quarter global phone sales declined 6 percent overall, but smartphone sales had grown by 26 percent since the same quarter last year.