My team and I are trying to build a Twilio VoIP-enabled app that can be added to both inbound and outbound GSM calls hosted by the OS using the 'Add call' / 'Merge call' tile on the call interface screen, so that, once connected, dual tone multi-frequency (DTMF) can still be used..
Despite our vision being clear and simple, we are struggling to solve this technically and so would deeply appreciate any wisdom anyone out there can offer!
Many thanks :-)
We have looked into using an API to play DTMF tones with Android but it only seems to be accessible via the native operating system which we don't have access to.