Sensitive Altimeter. This Android application measures air pressure using internal barometric sensor in the portable device and displays it on a three-pointer altitude indicator similar to the altimeter gauge in aircraft. Digital indication is also available.
It can take a long time. Some employers move very quickly, and others move very slowly. People have been hired three hours or three months (or more) after interviewing. Moreover, hiring nearly always takes longer than employers expect it will; you should generally double or triple whatever timeline they give you.
If you have another appointment set up, email the interviewer and apologize (even if it wasn't your fault for missing the call) for missing them and ask to reschedule. If you don't have another appointment or anywhere to be feel out how long you think you should wait. Waiting for over two hours is probably too long. At this point it is pretty safe to say that the interviewer forgot. Even if they remember two hours later, they probably will not have time to interview you.