You might have seen guidonnet levers on old French cyclo touring and camping bikes. They allow easy braking from the top of the bar, but they can't be used from the drops.
They are also ideal for city bars, like the VO Bellville and Porteur bars. You can brake from either the traditional grip area or from the front of the bar. This allows two safe positions in city traffic: a low aerodynamic position and a traditional upright position.
They are available in both road bar size (23.8mm) and MTB size (22.2mm). Price is per pair. They are compatible with caliper and canti brakes, but not V-brakes.