While most of the Gear S2's features work just fine when paired to a non-Samsung phone, Samsung Pay was off-limits unless your watch was paired to a Galaxy device. On the upcoming Gear S3 watches, it looks like that's no longer the case. The Samsung Pay Twitter account has confirmed to AC that the service will work just fine on the watch, when paired with any phone running KitKat or above.
To be clear, this doesn't mean you'll be able to use Samsung Pay on your non-Samsung phone independently of the watch, just that payments will apparently work on the watch without the requirement to use a Galaxy phone.
What's not clear is exactly how this will work. Obviously inputting card details on the watch directly wouldn't be ideal, so some sort of partner app on the phone would be needed. However, at present the Samsung Pay app is exclusive to Samsung phones. We've reached out to Samsung for further clarification.
It's also unclear whether both MST and NFC payments will be supported on the watch when paired to a non-Samsung device.
At the very least, though, it's a sign that Samsung wants to remove some of the barriers to entry for its payment service.