Along the same lines, I was thinking it would be cool to have a device that takes a receiver's sub output and splits it up to maybe six ways (for my own purposes, that's four subs plus two Buttkicker amps), but also allows you to set the levels independently of each other. Avoiding daisy-chaining and level loss, along with independent level calibration, among that many LFE-producing units would be my ideal.
It probably goes without saying, but if someone made a device like this, you'd want a remote control. For calibration purposes, you'd have the level controls for each individual unit, and for general use, you'd have the master volume level. While you could still take care of that one in the receiver, it might be easier to do on this remote.