A radio magnectic indicator allows for the visualization of the aircraft heading and QDM of the required station or destination. QDR is also available; just read the scale on the other end of the 'needle'.
The RMI is a powerful tool since allows you to navigate to any point on the planet. Most aircrafts have RMIs (or equivalent) as navigation equipment.
The mobile application provides for RMI functionality and also distance and EET. This allows you to practice and to master the RMI including to track and to intersect QDMs, QDRs, VOR radials; to navigate VOR/DME arcs, fix-to-fix, etc. Have fun!