I've got 3 in my S76 - one in the FMS box to drive the autopilot; a simple old Garmin that only gives basic info (too hard to take it out); and a new Garmin 196 moving map which shows airspace, topo and anything else I need. Two sets have antennas on the roof or tailboom, but all the 196 needs is its little suction-cup antenna, looking out the chin bubble! Doesn't even need to look upwards. Brilliant.
The 196, being portable, also slots into the Huey and the 47.
For basic VFR, though, something like a Garmin 195 or 196 moving map is plenty.