@gcluley the amcrest doorbells you can get off the shelf while they have their own service you can turn it off and it works as just a doorbell with standard password protected RTSP streaming (can use mplayer/ffmpeg/vlc) and save directly to a SD card. I think they don't advertise it to try to upsell their service but every one of their cameras i've tried can do this. I use them in zoneminder with no internet access on their network.