The MessageBird Voice Recording cURL Sample Code demonstrates how to record an inbound or outbound leg as part of the execution of a call flow. After a call completes, a recording can be downloaded as a wav file.
Google has apparently backtracked on the idea of allowing third-party messaging apps to access RCS on Android phones. Though RCS is a public specification, APIs are needed to connect messaging apps to the RCS protocols employed by wireless network operators. No API means no RCS for outside apps.
Cloud-based messaging app Telegram provides free, open and secure communication across any platform with automatic chat synching across devices. Telegram also provides a dedicated Bot API for building custom bots that users can interact with via messages and commands to perform predefined tasks.