With modern GPS systems and PDF's one can now have a bearing indciator pointing to wherever you want which looks to all intents just like an ADF RMI
True, but TBH I doubt that if the GPS was invented in WW2 anybody would be using "needles" today. The CDI/RMI/HSI bar or needle representation dates back to the goode olde days when a map type representation was technologically all but infeasible, and clever people invented all kinds of ways to enable planes to navigate relative to beacons.
Today, if really using the GPS, you would dial the inbound on the OBS mode of the GPS and track the magenta line (inbound) or the white line (outbound).