I just thought about this......
If you could engineer a LED torch (white light) to fit on top of a camera (on the hot shoe), you could provide some fill light in the day while using very wide apertures. This applies to close up portraits. Because torches are so low in light intensity compared to flashes, I dont think there will be exposure problems.
This is an alternative to flash sync limitations when using largish apertures.
What do u think ?