carib, thanks for sharing this -- this is a neat idea :)

Here's another Gmail hack I use all the time...

I have a filter set up in Gmail so that email with a certain keyword mailed to me gets auto-forwarded to my RTM inbox. My wife would never remember the RTM email address, or use it even if I added it to her address book, but it's very easy for her to add the keyword to any of her emails that she wants to get onto my todolist, and this way her suggestions (and a very few other people I am willing to add directly to my RTM) are waiting in my inbox when I review my tasks there.

Another use for this is when I email an article to myself about an issue I want to pursue further. I just add the keyword to my email to myself, and it goes right to RTM.

RTM and Gmail are simply great together.

Are you adding the keyword to the subject or body?
Since gMail supports plus-addressing, it might be easy to add "+rtm" to your gmail address... for example,

my.gmail.address+rtm@gmail.com

The mail would go to your inbox as usual, but would be easy to filter.

I decided on a message body keyword because that was easier to explain to other people, but you are exactly right that gmail lets you do the email+keyword@gmail.com scheme.