Seatpost or seatpost clamp with integrated daytime running light and camera. Battery in the seatpost to reduce bulk.
Similar for stem, light and camera slung under stem maybe so as not to interfere with head unit?
Helmet with integrated lights and camera, lightweight rechargeable, and AERO
Actually the Australian team developed such as shoe for the mixed relay events (which have very short swims, bikes and runs). Not sure it is commercially available though.
A screen that gets a live feed from an app on your phone. (Could be use for tons of things) this with the right app would replace head units and keep data on your phone
A bar stem combo with integrated batteries for universal connection of lights, electronic gadgets. (Batteries should be removable for weight saving)
A universal batterypack with different mounting and with the purpose of extending battreylife of lights, phone, di2 etc components