a nice feature for the EufyCam would be to link cameras/devices together. So for example if you have two cameras (or maybe a doorbell) monitoring a particular area then an activation on either device should tell the other device to activate too.
Some higher end equipment such as AXIS have these features already and I suppose something could be done with things like IFTTT but they have latency and rely on an internet connection.
Chaining of alerts should be configurable and not necessarily limited to two devices. also alert chaining should work in both directions.