RTSP (Real Time Streaming Protocol) IP Cameras are basically cameras using the RTSP/IP protocals to stream the output of the camera, meaning you can use your preferred viewer to watch, for playback. This is beneficial if you prefer to not use proprietary software.

Cams

Links:

https://f-droid.org/en/packages/com.vladpen.cams/
https://github.com/vladpen/cams

Pros:

Open source

Cons:

tinyCam Monitor

Links:

https://play.google.com/store/apps/details?id=com.alexvas.dvr

https://tinycammonitor.com/

Pros:

Cons:

Not free, £2.99 (as of writing this) to buy Pro version.

Limited features with free version.