http://www.emmicroelectronic.com/
EM6819 is to my knowledge only flash MCU that actually works from 0.9V
without external inductor (SiLabs 93x needs the inductor to start).
EM6819 has internal NO COMPONENTS voltage multiplier so it run from
0.9V external supply from 2MHz internal clock (1 MIPS). The internal
multiplier seems to have bad efficiency tought the current consumption
is over 400uA while with the DC-DC enabled is should be around 100uA
at same clock.
EM9201is another nice IC, at electronica we did BATTERY less unit that
transmitted and received data packets over 2.4ghz link from energy
harvested from the movement caused by the button press.
Antti
PS some of the rest of the info is under NDA unfortunatly