Let's see. according to https://www.lifewire.com/megabytes-for-one-minute-conversations-3426705 https://www.lifewire.com/megabytes-for-one-minute-conversati...

Let's see. according to https://www.lifewire.com/megabytes-for-one-minute-conversations-3426705 https://www.lifewire.com/megabytes-for-one-minute-conversati... , VoIP takes around 240 kb/minute, which is about 10GB/month. Lowering quality and simply not recording when no one talks, should bring that seriously down, say 1GB/month. Which is a lot today,but prices are falling rapidly. If it's mandatory by law, implementing it in hardware would make sense, which will also lower the battery drain. I don't like what I'm saying here, but recording and sending everything by law seems technically viable on the near future to me.