When I was in hospital for preterm labour they gave me one to help with my backpain. They got me to use it in the shower and rock backwards and forwards. My labour eventually stopped after all the meds. Not sure about its use for inducing tho sorry, it was good for my pelvis and back tho.
Its a good thing to start using it around the beginning of the second trimester to open up your hips, help baby get in an optimal position and help with your own posture.