Implementing real-time signal processing filters
There is a recent (2015) 150+ pages review called Smartphone-Based Real-Time Digital Signal Processing with lab codes. There are chapters like:


2: Android Software Development 
3: iOS Software Development
6: Real-Time Filtering 
7: Adaptive Filtering



  Real-time or applied digital signal processing courses are offered as
  follow-ups to conventional or theory-oriented digital signal
  processing courses in many engineering programs for the purpose of
  teaching students the technical know-how for putting signal processing
  algorithms or theory into practical use. These courses normally
  involve access to a teaching laboratory that is equipped with hardware
  boards, in particular DSP boards, together with their supporting
  software. A number of textbooks have been written discussing how to
  achieve real-time implementation on these hardware boards. This book
  discusses how smartphones can be used as hardware boards for real-time
  implementation of signal processing algorithms as an alternative to
  the hardware boards that are currently being used in signal processing
  teaching laboratories. The fact that mobile devices, in particular
  smartphones, have now become powerful processing platforms has led to
  the development of this book, thus enabling students to use their own
  smartphones to run signal processing algorithms in real-time
  considering that these days nearly all students possess smartphones.
  Changing the hardware platforms that are currently used in applied or
  real-time signal processing courses to smartphones creates a truly
  mobile laboratory experience or environment for students. In addition,
  it relieves the cost burden associated with using a dedicated signal
  processing board noting that the software development tools for
  smartphones are free of charge and are well-developed. This book is
  written in such a way that it can be used as a textbook for applied or
  real time digital signal processing courses offered at many
  universities. Ten lab experiments that are commonly encountered in
  such courses are covered in the book. This book is written primarily
  for those who are already familiar with signal processing concepts and
  are interested in their real-time and practical aspects. Similar to
  existing real-time courses, knowledge of C programming is assumed.
  This book can also be used as a self-study guide for those who wish to
  become familiar with signal processing app development on either
  Android or iPhone smartphones.