Can I build an addin for Gmail?

Is there a way I can create an addin for my Gmail account? Is GreaseMonkey the only real way?

I use Gmail for customer service, and I'd like to create a tool that looks up the customer and preps a response to them based upon who it is in my database... instead of looking by hand for the client and t开发者_开发技巧yping it out.

You can add gadgets (same as iGoogle and wave) and add them to the side bar in GMail, but you will not have access to the e-mails themselves. You could create small lookup forms and such, though.

I don't see how else you could do it. You won't be able to run your own app on Google's backend, so that leaves the client (with javascript and something like GreaseMonkey) and your server (perhaps communicating with the client via AJAX).