Another thought about 'spanking panties' - someone has proposed (and possibly produced) a fitbit-like exercise/health monitor, which can be programmed to deliver a slight electric shock if the wearer's heartbeat and respiration drop below a certain point during an exercise session, indicating that they're not putting in enough effort. With a little modification, 'spandex spanking gym shorts' could be a real possibility...!

As for the electronic hairbrush, my electronic toothbrush flashes red if too much force is used; perhaps the hairbrush could flash if too little force was used...