Let's suppose your internet connection is very unstable. Likely, after losing the connection you want to be notified when back online. Just run internet_tracer and do something without digress!
Using public some public IP resolution service: internet-trace -u http://www.myip.ru/get_ip.php?loc=.
By default, you will be notified when the first IP address found on a page is non-equal to 0.0.0.0.
It can also be used with DD-WRT router status page: internet-trace -u http://192.168.0.1 -w.
It is very easy to customize, just use internet-trace -h.
Tip: I highly recommend using --debug option until you finished with params configuration.