From my understanding, the P8P's video boost can't be done in the phone itself, but it's actually uploading the video to Google's servers, processing it there, then downloading the finished product back again. In fact, it probably uploads two videos, one at high ISO and one at low ISO to get the full HDR range.
For anyone who wants to take lots of videos, this sounds like it'll blow through your data caps very quickly.
I might be missing something here but nothing prevents your phone from simply storing the unprocessed video locally and wait for a Wi-Fi connection to send it to Google's servers?
That way you would still be able to keep shooting videos, it's just that they won't be processed until you get home.