I found [the Desktop Fluency System, no longer made] to be most helpful and effective, as well as highly versatile. I obtained my first model in 1995, and for the first month I used it my phone conversation (which often can be severely disfluent) was always fluent without exception. After the first month, I did experience a partial wearing-off effect, but the device still remained quite effective, and nearly always reduced my disfluency on bad days and enabled me to speak fluently on good days. The device has a variety of settings of different types of altered feedback, and can also combine them - so it was interesting to experiment to find what worked the best, and I changed settings around often. There's also a useful adjustable feature for self-practice which judges the intensity of one's voice onsets or phonation - I made use of this often in practicing fluency shaping targets. By far this is the best fluency device I've encountered. I did find, though, that it's not compatible with all phone systems.