Minolta invented the Senswitch for the Minolta XM (X-1, XK).
I personally think that was brilliant.

The X-700 and the XG series have a not less brilliant feature: a surface on the shutter release senses the conductivity of the finger and turns the light meter on. So the light meter stays on when your finger is on the shutter release and stays off (after 20 seconds or so) when you take your finger out of the shutter release.
The result is the same as the Senswitch: you can walk for hours keeping the light meter "on" so that you have it immediately ready but without wasting the energy during most of the time, when you actually just "walk".