Since 2017 I have been very busy with our new startup Voicegain. We have built a DNN based speech-to-text engine (ASR) and a whole platform around it.
The accuracy is pretty good – we are now pretty much on par with Amazon Speech to text. Here is blog post with our accuracy benchmark from just over two months ago. We will be soon publishing new benchmark with even better results.
Also coming soon is support for Twilio TwiML <Connect><Stream> which we think will be a better speech-to-text alternative for Twilio than TwiML <Gather>. We have already gotten some feedback from Twilio users and they are really looking forward to finally having support for standard speech grammars (GRXML and JSGF) on Twilio.