Digital Filter Designer is the tool for designing IIR digital filters on your Android device.

You can design Butterworth, Chebyshev, 2nd Order Shelf, 2nd Order Parametric, DC Blocker, First-Order Lag, Exponential Averaging filters and IEC 61672-1/ANSI S1.43 A-Weighting & C-Weighting filters with this app. The Butterworth and Chebyshev filters can be any order of your choosing.

The app will calculate the filter coefficients, save them to a text file (so that you can copy/paste the values into your code) and plot the frequency response. You can plot the frequency magnitude and phase responses and can select linear or logarithmic frequency scales. You can use auto scaling or manually set the ranges yourself.

This really is the most exhaustive digital filter design tool available for any smart device.