The TiVo Control API Reference
document on page 5 I think accidentally gives the wrong uri for "uiNavigate" operation for coming out of standby mode:
I didn't know about that one and as I suspected it takes you to the reboot screen where you have to confirm using 3 thumbs down, enter. So in next kmttg release I'm taking advantage of this by having a macro to implement a "Reboot" button from kmttg (the macro automatically includes the 3 thumbs down, enter sequence as well). This will allow me to reboot series 4 or later DVRs from anywhere I have internet access which will be useful combined with the existing "Network Connect" button.
The list of documented operations in the above PDF is VERY minimal and nothing I didn't already know about, so doesn't look like TiVo intends to give us extensive control of a TiVo with this initiative (hardly surprised).