This extension automatically logs you in to MyUW. 1.1: Fixed Icons
Just a quick extension (and by quick I mean one full day of work), I wrote up to bypass myuw's annoying "You need to re-login every 8-hours/ WHENEVER YOU EXIT THE BROWSER!" crap. When you download the app, you'll be able to enter in your netid and password, and the extension will take care of the rest.
Now, you can either trust me when I say that I don't do anything with your username of password within the app, but if you don't, you can always look at the extension code yourself and see that it doesn't send or receive data from outside the extension code.
Please read the disclaimer linked to from the options page concerning client-side security issues.