From corrosion to batteries and super-capacitors, mobility of ions at interfaces, a pre-requisite for many electrochemical processes, plays a key role in a great number of applications. In this paper we show for the first time that the Scanning Kelvin Probe (SKP) technique can be applied for studying ion mobility along any kind of insulator/insulator interface. As across these interfaces high biases can be applied, the determination of the mobility constants should be possible. Since for practically all kinds of interfaces model samples based on insulating substrate can be prepared, this is a break-through for studying ion mobility along any kind of interface, as well as mobility of ions adsorbed on a surface. While it has been shown nearly two decades ago that delamination of polymer/metal interfaces and also diffusion or migration of ions along such interfaces can be monitored in situ by SKP, no attempts have been made so far to apply this technique for investigating the mobility of ions also along interfaces between insulating materials. Here we show that this is possible. This opens up the use of SKP for a vast field of research that is of critical importance for many applications.