I'm constantly amazed at the cool things a smart phone can do. There are several spec. analyzer apps available but I'm wondering if they're really accurate enough to use for system tuning? I've tried a couple of these and I like Speedy Spectrum and Spectrum Analyze (for android) the best for features and apparent accuracy. My old Heathkit portable analyzer looks to be toast (yeah--I'm that old).
Any analyzer can only be as accurate as it's microphone allows. Good analyzers/DSP room correction systems come with calibrated mics. One has to wonder what the frequency curve might look like, of a telephone's mic.
They are as good as there mic's, which in most phones is pretty poor. Also, if the mic is not calibrated, the results you get can be misleading. So, in the end it really depends on what you are using the app for. Certainly the results could not be called 'professional' standards.