The handsets that can gain access to Sprint’s push-to-talk service as of now are: Samsung Galaxy S4, Samsung Galaxy Note 3, Kyocera Hydro Edge, LG Optimus F3, LG G2, and the newly-launched LG G Flex. According to Sprint, other three smartphones will also be compatible with Direct Connect in the near future: Samsung Galaxy S4 Mini, Samsung Galaxy Mega, and Samsung Galaxy S4 with Sprint Spark.
The Direct Connect Now application can be downloaded for free via Google Play. Sprint’s Sprint Direct Connect service is available at no charge to customers using select plans, but it can cost and additional $5 per month on some plans. At the moment, Direct Connect supports push-to-talk on Sprint’s LTE network, and has “triple the square miles of coverage" compared to the phased out Nextel National Network.
sources: Sprint, Google Play