TP Link have a bunch of reasonably priced surveillance cameras that link using wifi and your internet router via mobile/PC app, so you can view on phone, tablet, PC, etc. Their system is called TAPO. Link:
https://tinyl.io/6cvC
The app allows you to access the cameras from any internet-connected location. Cameras are good quality, easy install and come in weatherproof models if you choose.
I have two that allow me to monitor inside the obs and a second that monitors the outside environment, in colour and day/night IR vision as well, from anywhere on the planet that has reasonable internet.
You can no doubt find similar from other mfrs, but my user experience with the TP link stuff has been great.