Here is something I found interesting on the web. Retroshift marketed for cyclocross,but I could see this application used in different riding set-ups. Here are some to name a few:
Updating and old bike
I am sure the list could go on. What I think is cool about this set-up is your ability to shift multiple gears at one time. They show you in the video how it shifts. I would think this would be serviceable in the field. Not much to fail! Cool idea, I hope they do well!