TENS (Transcutaneous electrical nerve stimulation) machines are devices that emit low voltage current to stimulate nerves. They’re often used as a means of providing pain relief (in sore muscles or tension headaches, for example) and yes, there are TENS machines for your pelvic floor as well.
UK based company Tenscare offers a line of Pelvic Floor Exercisers which send a gentle stimulation to your pelvic floor through a vaginal probe, thereby working your pelvic muscle for you with the intention of enabling you to develop your own muscle control. Some of these devices include Biofeedback, so you can measure how well you are controlling your pelvic floor muscles.