I have a computer whose WiFi adapter software does not install an icon on the system tray that would allow me to enable/disable the NIC's radio. Every single NIC adapter that I have used thus far has come with this utility.
There is an OCX called "System Tray Icon". With the Icon on the tray, you can use the built in events as in leftbuttondown
Which then could invoke a ShellExe() to start your application. Then use the Terminate program API to stop it.