Re fitting FLARM to IFR helicopters, they certainly are in Switzerland/Austria since an auxiliary function is obstacle warning of cables strung across valleys, as well as avoiding all the FLARM equipped gliders. I believe it is classed as a portable device, and has a temporary fitting, similar to the portable Garmins that seem remarkably common as precaution against fitted equipment failure in other certified aircraft.
FLARM is the little box above the EFIS
As far as using FLARM, a full functional description appears on their website. In real life it's switch on (its a secondary function of my flight recorder, with a small display fitted in both front and rear cockpit.
Nearby FLARM equipped aircraft are indicated by an LED in the appropriate 'clock' direction, with an above/below indication of the closest. Near but no 'threat' re green.
If the software thinks a collision risk exists, it flashes the LED RED and with increasing risk flashes faster and lights ajacent LEDs. It also beeps to alert you if you aren't looking (although the display is so small it is easy to position on the sight line) and the beep can be fed into the aux port of an intercom (but obviously not on a certified aircraft - that might be safer, but you can't connect a non-certified object into a certified installation).
Similarly, 1090ES ADS-B involves not only an extended squitter Mode S transponder, but also an aviation certified GPS, costing an order of magnitude more than a non-certified one; cost weight and power.