A lot of people have done it. I'll see if i can dig up some links. I've heard the mod puts a lot of stress on the motor, causing premature burnouts. One thread i remember seeing showed a more powerful RC motor that works well.
If you have a Halo Too, it's sound activated, so that'll do you well. Anything with eyes can be rigged up to the switch in any electro (or Intelliframe). That solves that issue.