mm_flynn have you got some links please?
Its not to argue about it, its so I can use them as case studys.
I don't doud't there have been at some point. I would reckon though there have been just as many with all the bells and whistles. On european machines we have EGWPS which gives some protection as long as the crew listens to it.
The fact is though that installation is about $10k and only requires one update subscription to be BRNAV compliant. The Garmin 530 option is two units two subscriptions and a mod to get the radio stacks changed and most planes just don't have room to shoe horn the units into the instrument panel where they can be used and seen without a major rework. I would imagine its even more of issue with rotary.