Should ping www.google.com every second.
It should display a connectivity icon in the taskbar. I will provide 3 icons, green, orange and red.
The icon should be green if the ping reponse is OK and under 1000ms in the last 5 seconds.
The icon should be orange if and any packets lost (no response or response times are more than 1000ms) in the last 5 seconds.
The icon should be red if all packets are lost (no response in the last 5 seconds)
Possible caveats to tackle: It will need to make a dns lookup initially to resolve google.com. The program needs to cope that if it is initially run with no connection to the internet, that the lookup is done again until successful resolution.
It should make little to no CPU activity and not block anything on the system.
www.codedesign.com has a bunch of example stuff which you might be able to reuse.