Mobstacle: An individual or group of individuals who walk slowly due to focussing on their mobile phone or other mobile device and generally making it difficult for you to pass them, hence you are blocked or slowed down by their nuisance.
Warning - A mobstacle is prone to unexpected changes in direction or erratic gestures, requiring a wide berth by all normal pedestrians.
I missed my bus because I was stuck behind a couple of mobstacles!
The noise one makes at the end of a particularly satisfying stretch.
The typical stretch that leads to a Nuuuurg is usually a Sunday morning stretch where you have woken up naturally after a very fulfilled sleep. The noise is sometimes involuntary, however also can be called upon to achieve that extra bit of satisfaction from the stretch.