If you’re talking about electromagnetic fields, any electronic device has one so all baby monitors will also have one. There has been some research into the effects of EMFs but as far as I know nothing has been directly linked to small/weak EMFs like those generated by household electronics.
If you’re wondering about electromagnetic radiation emitted by the WiFi radio that should be just as safe as any other cell phone, tablet, or laptop, or baby monitor that has WiFi.
That being said, some people have had issues with the audio or the whole stream dropping out when using it for long periods, so if you want an always-on solution you might want to look at something that has a dedicated screen. You could also use an audio-only monitor for always-on monitoring and a Wyze Cam to check in periodically. I’m a few years past needing baby monitors so perhaps someone else who is currently in that situation can share some of the Wyze Cam baby monitor pros/cons and usage tips.
Edit: Here are some relevant topics discussing baby monitor usage with some user experiences: