The Aerial interface allows you to charge RF-enabled items in the player's inventory.
Perhaps this could be extended to also charge OpenComputers' Nanomachines in the player's bloodstream
Power conversion rate appears to be 14.3:1 (from here)
I looked through the OC API and found the methods required:
li.cil.oc.api.Nanomachines.getController(player)
controller.changeBuffer(powerChange)

It's a nice idea, but I'm not doing any more feature work for 1.12.2 now at all. If OC makes it to 1.15/1.16 then I'll definitely keep this one in mind, though.