Support leaving audio message, which is already the case if you have an audio recorder with specific intent on the Android client (Record audio message) => Already present on master
Add a custom recorder if no intent is available. Should be easy to implement, but not present
Resend as soon as possible the file (which already have an issue on this gitlab so I consider this as out of scope here)
Sync between devices (which has several issues on this gitlab, so I consider this as out of scope here)