My 2 cents... a spectacular dress watch as beautiful as these - http://www.tagheuer.com/int-en/home - sporting physical hands and limited electronic display, crammed with sensors, ULP Bluetooth, inductive charging and completely and utterly sealed. The time at a glance, my iPhone can and does, do the rest.
Would have thought 'curved' rather than 'flexible'. Sensors would need to be in close proximity to the skin. A greater number of sensors or sensor area would require more contact area. I still favour dress watch, less display, as we have previously discussed.