I've seen the e-bike kits on that end of the forums where you just add a rear wheel w/ a motor on it and stuff a gigantic battery on your rack. $500~$1000 to install it on any old bike it sounds like. I'd like to give it a try but the price tag is a little steep for what'd essentially be a toy for me -- not enough hills nor distance to make the investment and troubleshooting necessary worthwhile. Still might consider it if I get another upgrade itch, though!