There is one more option that should work, but it is expensive and pretty clunky.
You can get a Lutron maestro single gang device which can control both the fan and the light kit using IR. ($100)
https://www.amazon.com/Lutron-MIR-LFQMT-WH-Maestro-Dimmer-Control/dp/B0017OAWQ0
The switch communicate to the fan controller via Lutron’s proprietary frequency, but the switch itself can be controlled with an IR remote. It comes with its own remote, but you can also use harmony with it.
Once you have that set up, you can then use a harmony hub to control the Lutron light switch. ($100-$130 for the harmony depending on if you get it on a deal. Best Buy puts it on sale pretty often.) because IR is line of sight, the harmony will have to be in the same room as the Lutron switch.
http://www.bestbuy.com/site/logitech-harmony-home-hub-black/1483019.p?skuId=1483019
And once you have that working you can then activate the Harmony activities with SmartThings.
Not all fans will work with the Lutron switch, but you can check with Lutron on compatibility.
Oh, and it won’t work with LEDs – – you’ll have to use halogens or incandescents.
So, expensive and clunky, but it does offer one more option to consider, especially for older retrofits.
Talk to Lutron support if you have any questions about how to get the fan working with their switch. But once you do have a fan working with this Lutron switch, getting it to work with harmony and then smartthings is pretty straightforward and will not require any additional wiring or devices except the harmony hub, which can also be used for AV control in the same room.
To be clear, the 2 zwave device method gives you a lot more options, including the kind of bulbs to use, and I would always recommend that one first. also as @MikeDL points out below, since this method uses an IR connection you won’t get feedback if someone uses the wall switch, so the fan could be on and your Home automation system wouldn’t know it. But if you do have a particular set up where the zwave method just isn’t going to work for you, and you need a one gang solution, this is another possibility.