You may find it quite PITA, due to google changing their logging method quite frequently. They do it, because they like break programs like gMail Drive (sometimes, new version of Gmail drive, just changing logging mechanism arrive every few weeks), so your application may be affected also.

I tried to check if Gmail Drive is Open source (so you could examine login method they use), but unfortunately, license isn't stated anywhere, and it's being released as binaries, so probably it's freeware closed source. Still, I've heard of phpGmailDrive for GNU (tool working just like gmail drive, but linking many accounts into one virtual big account) - You may want to search for it, it may be Open Source.

Hope it helps and is at least relevant to Your troubles

/Estel