In 2010 I started a company called Other Number which developed a virtual PBX that used Twilio for controlling phone calls and allowed people to set up call flows with menus, timers, voicemail boxes and many other features.
Users could also dynamically provision phone numbers from all over the US as incoming numbers and connect them to their existing flows. This was a huge advantage over hardware PBX where you’d have to get the phone company to set up the number for you and they’d charge a fortune.
We even had a conferencing system that allowed the host to mute attendees if they were being noisy which was not a common feature in 2010!
Ultimately, the product was doomed because the market became commoditized and Twilio open sourced a product that did most of what we did so that anyone could have it up and running very quickly.
We switched to consulting work and built enhanced versions of our original vision using OpenVBX as the base but with custom plugins for transcription APIs and delivery systems.