Most likely you will need some kind of IR blaster, and exactly what commands you will have available will depend on the IR blaster you choose.
I like the harmony home hub remote. It has decent basic integration with SmartThings, and a new integration is in beta which the testers say expand the capabilities quite a bit. However, you don’t get voice volume control with this integration. Basically, it’s on, off, and switch from one input to another by voice, and then you use the regular handheld button remote (or the Harmony app) for everything else.
I am quadriparetic so voice control is very important to me. I use a combination of smartthings, the harmony home hub (as the IR blaster), IFTTT, and echo to give me natural language voice control for things like
Turn on the TV
Turn on the Roku
Turn on the DVD
Turn power off
Then I would have to use the handheld harmony remote or their tablet app if I wanted to adjust volume or use fast forward.
So it’s not total voice control but it is very nice. More discussion and examples in the following topic:
Because Harmony has its own iPad app, you can combine that with what is called “switch control” or with Apple’s voiceover so that you could get better hands-free control of every button on the Harmony remote. It does work, but it’s very tedious. It’s the way quads use touchscreens when their hands don’t work. But using those methods it can take you literally 10 minutes to change the volume.
So, the Amazon echo integration gives you really nice natural speech control for just turning the TV on and off, or switching to a different Device like a Roku or a DVD player. But at the present time there is no voice control for the adjustment buttons like volume control or fast forward.
So it all comes down to the exact use case you’re trying to solve.