I have seen demos of one type. And use another.
There are basically 3 types.
1: Your basic reel, just roll up the cord, nothing special (I have several)
2: Cord reel, this unit either has an "outlet" that rotates with the reel or slip rings and a fixed outlet or pigtail, I don't like them, slip rings are prone to failure
3: Power cord retractor systems. These are NOT cord reels, and are likely best for your situtation, Was looking at them last week, round $500 more or less depending on the cord (more for 50 less for 30 if memory serves, however I did not pay that much attention as I can wrestle the cords for that money)
These units consist of a motorized unit which either pulls the cord out of, or into, a box, inside the box the cord coils on it's own, it's not reeled in and out so there is no need of slip rings, the RIG end of the cord can be hard wired to the rig
Looked good, don't know how well they work but the dealer demonstrates many times per show and never has a problem.