We have this one and it suits our needs. We bought a WiFi camera to use as a monitor as well, but we found ourselves constantly checking on him and it was unnecessary so we returned it.

This is what I've used for my boys:

https://www.amazon.com/dp/B007NG5UF4?tag=mlb-deaf-monitors-20

It vibrates when they cry. I basically fall asleep hugging my monitor.

I picked up a Foscam 8921W for video that we view on our smartphones. We use this vtech monitor for audio. The total cost when I got them was $180, though the Foscam looks to be way cheaper now, so it's only $120ish for the package.

Works great, no complaints.