Under Armour is making a major play to gain a foothold in the fitness-tracking market, which is led by the likes of Nike, Fitbit, and Jawbone. The company has snapped up MapMyFitness for $150 million, giving it instant entry into the blooming activity-tracking business. Its not immediately clear how Under Armour will specifically use MapMyFitness, but it is readily apparent that it will take advantage of the platform for future tracking devices. With MapMyFitness valuable community, the company may be able to become a major competitor to Nike, which launched its first tracking devices back in 2006.