I went to TEDxCam and it was a good experience. I think one problem with the TEDx conferences is finding out about them, I only found out about it by word-of-mouth. It would be nice if I could go to some website and subscribe for notifications of say TEDx events occurring in the UK.
We list all TEDx events at http://www.ted.com/pages/view?id=348
But I see what you mean about auto-notification. If you could sign up with an account for TED.com, input your current location, and automatically receive updates from nearby TEDx events, would you use it?