“didn’t Google recently say that no other automated mail checking tools were to be used except for their own GMail Notifier”

Yeah, they did say that, but only because the API wasn’t stable at the time; lots of the early GMail checkers were glorified screen-scrapers, bandwidth heavy and suchlike.

I think that soon GMail will be open to IMAP access too (and hence about a million little “check my IMAP” applications. They opened up POP access a little while ago (which works nicely, automatically leaves messages on the server, and if you send using their SMTP server, it automatically copies emails you send using your POP client into your ‘sent items’ on the web interface), and they’ve hinted strongly at IMAP. From the POP help page:

“Gmail doesn’t currently support IMAP access. As part of our ongoing commitment to give our users easy access to their email, we have introduced POP access. We look forward to announcing more features as they become available.”

–Jon