BlueKey

You can also achieve this with nvtop and have a pretty TUI (terminal UI).

Session is cool but sometimes unreliable in the delivery.

SimpleX is also quite interesting. But I don’t use it enough to say something about the reliablity.

But as you mention, NaN propagates.
So at checkout, your wallet will become NaN, as the shops money balance. Then it will spread to your bank account and before you realize what happens the whole banking-district is in flames.