From some experimentation, I wonder if Tesla isn't blocking third-party apps, but is just more aggressively rate-limiting the requests. I reset my logger to only update every 10 minutes and it's been running fine for over 24 hours (3 503 responses, but that's pretty normal). This is with the old portal.vn API, FWIW.
It could be a red herring, but figured I'd mention it.
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Wayner, check out the wiki here with a few links to libraries:
REST API Tools and Apps - Tesla Motors Club - Enthusiasts & Owners Forum