Found nothing similar via search or compendium, so apologies if I missed it.
Redstone-coated cable insulation / Redstone doped paint.
Not sure how possible this is, but the basic idea is to allow cable insulation to be either doped or coated with redstone, or add a redstone doped paint, which would also allow glass cables to be redstoned. This would allow this cable block to carry, in addition to EU, a redstone signal to adjacent redstoned wires or redstone-able blocks.
Several potential methods, rubber+redstone = redstone insulation, insulated cable+redstone = redstone insulated cable, apply redstone with rightclick, new cutter mode or redstone painters* (painter+redstone+optional dye).
Reactor connected to MFSU via redstone insulated cable. MFSU set to emit when full, which will disable reactor until there is room in the MFSU.
* Granted, this would require doubling the number of painters, and deciding wether or not this could be applied to CF blocks, but makes the most sense to me.