On the Meraki Go App, click on the hardware icon, then select your firewall, and scroll down to the troubleshooting section. You can test the performance to any website you want.
If you are looking for a system that will send you emails when performance to any set of sites drops below any threshold and let you know where the problem is (LAN, WAN or site), a Meraki Insight license with a MX series firewall it a great solution.
Let me know if you want to see a demo of Meraki Insight.
Dave Anderson