Humour me.
In the good old days Shimano road STI's were double chain ring only so some bright spark (Mr Erickson?) invented something to allow them to use 3 chain rings.
http://www.sheldonbrown.com/gloss_e-f.html
Finding them now seems impossible so who can come up with the simplest alternative?
Got to tension cable enough to move it across one chain ring. One alternative I have though about is a down tube shifter running a second cable to the front mech. Cable tight equals normal setup with modern double shifter and then slack drops mech away to inner ring.
Maybe there is a common or garden "thing" that could do the job or be bodged. A normal cable adjuster would take way to many turns to do it so it needs very coarse thread. The Gizmo does it in less than one turn.
Why? Well I like my hydro brakes and I cannot abide huge rear sprockets so a 28/38/48 triple with a 32 rear makes a nice touring set up.
Use your imagination.
Or sell me a Gizmo