Interestingly, Bromptons[0] using Sturmey Archer internal hubs, and I believe you can buy an upgrade that puts a derailleur on the front, to double the number of gears.
The owner of a bike shop I used to frequent had a Moulton (one of the old space-frame ones) with a 5-speed hub and a derailleur on the back and three rings on the front. He said he wanted to see just how many gears he could actually get on one bike.
