Here's one of our plants in Canberra which is past 3MW now, and is the first of its kind to be approved to bid into our fast frequency stability markets (where you have less than a couple of seconds to respond).
It's transforming a complex heat/fluid/mechanical system issue into a computer network and security issue. Usually the home network internet access market is very concentrated so a failure there could make the VPP unavailable. Solvable by putting control servers in various places and having each box connecting to multiple redundant control servers hosted with diversity and redundancy in mind.
Also ISM low bandwidth IoT radio technology like LoRa and sigfox might help redundancy too.
Might become important is VPP grows beyond handling rare grid events.
One nice thing though is many of the stability services (such as balancing frequency) can be detected locally and therefore centralised dispatch and comms aren't necessary. All of our household systems have high speed metering attached (sampling at 20hZ) and when they make a frequency measurement outside the normal operating range (48.8Hz - 50.2Hz) they discharge/charge respectively. This means that when there's an event we have all the systems reacting in a way that looks coordinated, but is actually just syncronised (as they all essentially have the same input -- grid frequency), so services like this are extremely resilient.
Presumably you need comms later to add up how much frequency support you ended up providing, for market settlement?