I've been thinking about making a top cap for a Genesis style atomizer that doesn't leak. Something with an adjustable airhole, a bunch of holes in ascending diameter in a ring, similar to this one:
Helios Rebuildable Dripping Atomizer - RBA's. You would be able to spin the ring further though and close off the airhole all the way to avoid leakage.
Further, I think it would be awesome to then have a groove in a particular part of that ring on the opposite side of the airhole that corresponds to a switch that would move up the top cap vertically and eventually plug the bottom of the drip tip. The switch could only slide up when the airhole on the ring is in the locked position, and it would also work to keep the ring in place until it is disengaged.
Kind of hard to put what I'm envisioning in my mind in to words, but I hope you get an idea. It would be great to make a cap for a genny that you can put in a pocket or purse and not leak.
Oh, and I'm a real big fan of Zen's Z2 system. I really hate the 510 connection, went through too many devices when I started because of cheap Chinese construction, threading issues, etc. It's an open source spec, and I can't wait until more devices are available for it.