To connect Jetpack in your local installation, you'll need a way for WP.com servers to reach your server. That can be done in a number of different ways:
- You can open your router's ports and use your public IP
- You can use some kind of Dynamic DNS provider.
But these options fall short of ngrok, which is a "localhost tunnel". It basically allows the Internet to hit a local port on your machine without worrying about ports or IPs.
As long as ngrok is running, Jetpack / WP.com will be able to communicate with your local site. This will allow remote modules like Site Search and Manage to work.