I'm sure it has been done before. But I thought I would post a bit about the process.
I had a couple manual vacuum hose reels that came with a truck I bought.
The conversion was relatively easy. That being said, if you have zero welding or fab experience this might be very hard for you.
We bought 2 DC motors $180 each, enough for two reels
1" channel-20' section
2" angle iron
6" x 1/4 plate about a foot
Misc bolts for attaching motor to bracket
Roughly 12' of link belt, about $60.00 per reel
1.5" 5/8 pulley $10.00
Instead of a big push button momentary switch, we went with a standard Ford starter solenoid. I love the Butler electric hose reel push button, so we bought some gooseneck flexible tube, and put a small push button on the end. I soldered the wires to the switch, but you can buy momentary switches with both wires already attached on Ebay