Flying ATPs up in the Scottish Islands, we were quite frequently *asked* if we would take part in a D&D exercise.
Turn the transponder off, practice Pan on 121.50 on box 2, and state our last known position ten minutes previously. They would give us headings to fly, pin us down with DF and call us with their best estimate of our position. Sometimes they were spot on, sometimes hundreds of miles out..... in that case, we'd do it again. It certainly wasn't for our benefit, so it obviously cuts both ways.
And anyone who has 2+ radios and doesn't monitor 121.5 is asking for trouble. ..