Lovense is a brand of interactive remote control vibrator. It reacts to the tips sent by viewers to the performer. The bigger the tip you send, the greater the intensity and length of the vibrations for the model.
You will see if the model is using a connected Lovense by looking first at the landing page image of all the models. You'll find the Lovense logo there.
When you click to join a broadcast, you'll see this note on the chat screen:
You will also see the Lovense logo and under Send Gift, you'll see Activates Lovense
There will be a list of the costs of each different intensity and duration of Lovense activation, found within the Turn Me On section.
Each model will set their own rates, so each would be different.