Even though I’m a huge HomeKit fan and have also requested this, I think you have a misconception about how much Sense could learn from HomeKit vs the existing integrations. HomeKit doesn’t supply high resolution power monitoring data (like the supported smartplugs) and even the on/off data can be offset by several seconds, one way or the other from the actual on/off power signature of the device. I have a couple of HomeKit-enabled Elgato Energy smartplugs that support power monitoring but they only provide data on an every 5 minute basis (with lag) vs. once every two seconds like the HS110.
It might be cool if there was a way for HomeKit to feed power data to Sense, like the Hue hub integration does, but that’s not in the cards today.