GBEBZ
The bigger aircraft use DME as part of the system redundancy the Boeing 737-800 has five !
Two are crew controlled, the other three search out the best DME stations for position fixing ( data from all five is used) this is part of the way that the FMC assures the navigation quality of the two GPS units and maintains the system accuracy when the GPS system quality falls below IFR limits.
What the Avionic fit in GBEBZ enables you to do is exactly the same ( if a little less automatic) you can continue IFR flight safely if the GPS fails.