I had a membrane sweep with my Lachie pregnancy. Basically (sorry if this sounds icky) the OB uses his fingers to 'sweep' an area which breaks membranes. The idea is that it is a gentle way to encourage labour to start but is not an actual induction. I had mine at midday on a tuesday and by wednesday night I had Lachie. It doesn't involve breaking your waters. I would advise you to take pads with you as you will find you will bleed afterwards. You may also be a bit crampy but I am unsure if that is because I was in early labour or due to the sweep. When my OB did mine I was already 3cm dialated.
I wish you all the best and look forward to reading that you have had your bub.