For this purpose we have a special device and a minor change approval that allows for installation without limitation to VFR certified aircraft. The unit is called TRX1500A. It has the same functions as the PowerFLARM but features a special Interface (called ARINC429) that allows for connection to professional certified avionics systems like the GTN or G500 series from GARMIN.
More Information about the device: http://www.air-store.eu/en/TRX-1500A+-+Professional+traffic+warning+with+ARINC-429+Interface,i5.htm
The TRX 1500A can be connected to certified devices with this minor change approval, it is not limited to VFR certified aircraft, and also exterior antennas are included: http://www.air-store.eu/en/Installation+Approval+for+TRX+Devices.htm