Use Text To Speech On A Voice Call

Is it possible to use the text-to-speech engine to send a message through a voice call? Like an answering machine. It's also possible to monitor an outgoing voice call to read out

Solution 1:

During a call, speech generated by TextToSpeech engine won't be audible to the other end of the call.

Solution 2:

No. In typical android phone designs, the in-call audio bypasses the processor on which linux/android are running, so you can't directly inject anything into it.