Green!
This is a really cool idea. I've thought for a long time that passwords were the next best thing to broken as a means of authentication so any developments would be very welcome. You've certainly got the right audience to be trialling this sort of technology.
If I can make a suggestion (though I fully appreciate that this would cost time and money but just getting it out there. Might plant a seed), a yes/no app would be even better than an email link. Try and log on to something, then press a button on an app, and in. Maybe behind a PIN code stored on the device or something?