If you want a simple realtime indicator showing ping result on your top panel in GNOME, then Ping Indicator (by trifonovkv) is exactly the Shell extension for you. It's really simple, just always show you a realtime value of a ping command to a specific destination. It helps you simply to determine whether the network is up or down. It won't be overrided by any application window, to compare it with any desktop widget. Here how to install and configure it. This tutorial is intended for GNOME Shell users only.
Follow our instruction to install GNOME Shell extension. Once installed you will see a new entry in your top panel showing ping output values.
Basically, once installed, Ping Indicator will be shown on the top panel pinging Google DNS (126.96.36.199). You may change this behavior to your preferred host by:
(1) Right click the Ping Indicator on the top panel > Settings.
(2) Change the interval value into 1 second. This will make it more realtime. If you wish another else, its up to you.
(3) Change the destination host into an IP address or a domain name you desire. For example, enter www.gnu.org. Press Enter button after changing the address.
(4) Turn on the beep when timeout option. This will make sound beeping when the destination is unreachable or by other words, when your network connection is down. It is quietly useful.