A manual selection of the Mobile Network Operator (MNO) to be used on a mobile device is possible through the respective user interface. Furthermore, mobile devices can be adjusted to select automatically the MNO based on the strongest signal strength, among the list of those MNOs the Subscriber Identity Module (SIM) card is allowed to be registered with. However, so far in modern mobile operating systems, such as Android and iOS, there is no available method in the public developer’s Application Programming Interface (API), which allows for an automatic and on-demand selection of the MNO by third-party applications. Recently, various research approaches assume the existence of an automatic and on-demand MNO selection mechanism to achieve different goals, such as breaking the termination rates monopoly (AbaCUS) or minimizing the non-ionizing radiation of mobile/wearable devices. The interest of such a mechanism has been raised three years ago by the Android developers community. Thus, this work here presents an automatic and on-demand MNO selection mechanism, that has been designed and implemented on the Android platform. For evaluation purposes the energy and end-to-end (e2e) time consumption while switching among MNOs using this mechanism is evaluated and as an applied example the data consumption of AbaCUS signaling messages is measured.