It's when you combine sex toys with remote control, typically over the internet.

Applications include obvious things such as synchronizing a vibrator to the action in an adult video to enhance immersion, kinky play like letting a partner or audience member control a tactically placed vibe, or even humorously creative stuff like using an artificial vagina as a video game controller. There is some quite interesting and fun work being done in the area, such as the Buttplug protocol.

Based on your username you might already be familiar with all this, though.