The Gear S3 connects to any Android device running Android 4.4 or newer, with 1.5 GB of RAM. Often rumored iOS support, it appears, still isn't available.
There are two key features to the S3 line. One is the inclusion of an LTE wireless connection with the Frontier model. Using AT&T, Verizon, or T-Mobile networks, a Gear S3 users can place phone calls and reply to messages without a smartphone or Wi-Fi connection nearby.
Additionally, the Gear S3 is the first wearable device to feature full Samsung Pay support. Not only does the Gear S3 offer NFC payments much like the Apple Watch currently does, but Samsung has included its MST technology into the watch itself. Using MST, Samsung Pay users are able to transmit payment data to nearly all credit card payment terminals.
For the last two years, all Samsung Galaxy devices have offered Samsung Pay complete with MST capabilities.