Yes, as of 2011, the FAA is requiring that you obtain a Supplemental Type Certificate for an ADS-B "Out" installation on any aircraft. Several OEMs and engineering companies such as Southeast Aerospace are developing STCs to be processed and eventually approved by the FAA. The FAA has not advised if future ADS-B installations will be possible through FAA STC AML (Approved Model List) although it is a good probability once several STCs have been issued.