does the current version of the Smart Home SDK implement a 'time-delay' or 'time-state' controller ?
Like "Alexa, turn on the thermostat at 3pm".
Or do I have to add a custom voice model for this?
There is no functionality to add scheduling to smart home devices, so a custom voice model would be suitable. Note that specific interfaces have this in-built, but you would need to check the relevant documentation for details - check out the following documentation on scheduling with thermostats:
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