See the AP760 in action. It is measures accurate inclination while drilling (rotating) and real time rotation detection with accurate RPM reporting.
MWD – Measurements While Rotating
“Measurement while drilling” (MWD) refers to the real-time data relayed to the drill operator during the drilling process. The MWD operator measures the trajectory of the hole as it is drilled. This information is then used to drill in a pre-planned direction into the formation containing the oil, gas, water, or condensate.