The use of technology to enhance fluency can be divided into two methodologies - Frequency Altered Feedback (FAF) and Delayed Auditory Feedback (DAF).
Delayed Auditory Feedback works on various platforms including certain mobile apps (it started with Reel to Reel tape delay). It is the easiest of the Altered Audio Feedback sounds to reproduce, however it has limitations. There is defiantly a place for DAF on a mobile especially for low cost evaluation purposes.
Frequency Altered Feedback is far more complex to reproduce. VoiceAmp uses this method which includes noise suppression and other algorithms to provide a superior solution. The technology used by the VoiceAmp device cannot be replicated using mobile apps.
Some point to consider:
VoiceAmp is continually improving existing technologies and exploring new techniques to improve fluency. We value your feedback. For technical support, please contact us.