Let the tenants know that you have heard of some crime in the area so you are going to be monitoring.

Knowing that, they should have monitored him until he was gone.

I have similar cameras monitoring my other 10 units.

I'm going to monitor the activity of her unit for this month, till her lease expires.  

I already use Google Drive/ Work.Any suggestions for tablets, monitors etc?

Monitoring the work of a property management company would take time and energy too.

You can set up more appropriate gathering spaces through landscape/design/providing lawn chairs/etc.But, really, it is very difficult to monitor and enforce guest policy, so learn to deal with it.  

Monitor market rents and vacancy rates then react accordingly. 

.- Always interface between the tenant and the repair person to monitor work being done.

Even so, I would create an addendum to the lease that indicates that the tenant is responsible for maintaining the equipment, paying the monitoring fee and uninstalling it when they vacate.