How do you use PIP mode?
Using a keyboard or remote, send the "P" key. (But not on the Chromecast with Google TV (CCGTV), as the windowing code does not seem to be present in the system, even though apps can set the preference to allow themselves to be windowed.)
How about using a tivo remote with ts4k?
Then you need to remap a button to send a "P", as there is no "P" key on that remote.