Unfortunately TiVo's normal standby doesn't actually power all too much down - since it still may be recording in the background - so nothing can be determined from the plugin (at least on the Series 3 and Premier units). Some of the other-branded ones seem to have a "STANDBY" command, but not sure what it will do (and I don't know if it will tell the plugin that its current state or just able to put it in standby). Not sure the plugin will work with off-branded units, though.
If it goes all the way off you might see the isConnected state turn to False, but sometimes those connections don't even realize that they are no longer connected until something "forces" a refresh (e.g. trying to communicate).
At some point I may look further into using a different interface to augment the current functionality - but that has some issues with the version of Python that we are using and is not officially supported by TiVo for 3rd parties. The former is a major obstacle, the latter just makes it a little bit harder.

Even then, I haven't ever seen a standy query, but it may be that I just didn't recognize it.
If being able to try to put it into standby is something you would want (even if can't read status) I can try issuing that STANDBY command "manually" to by box and see what happens

Adam