Increasingly, new players are turning to microphone-using apps rather than dedicated hardware tuners. Although they can be useful for tuning an acoustic in a hurry, for practicing or concert use these are insufficient. Background noise and ergonomics mean that the microphone often can't get an accurate input. Besides, having an 'always on' option on the floor is far more reliable when you need it.
Google also recently launched its new browser-based Google Tuner. While you have to strike the strings pretty hard for them to register, it worked consistently in our tests against the Korg chromatic tuner and TC Electronic’s PolyTune app. The main interface is pretty user-friendly, too. Google Tuner would be a useful backup if you ever forgot your hardware tuner or found yourself out of batteries, but we would always advocate owning a dedicated tuner.