The only thing I can think of is a water heater that knows when power is cheap and preheats water hotter than it needs to be so it's available when you need it without using power ... I guess?
The opportunity to reduce carbon emissions is pretty massive when done at scale, because water heating accounts for 25% of home energy use in California.
In general, there is a big rush of companies, both startups and established, into the DER space right now, I suspect because of both the relatively low cost of entry and the high value of the grid services (frequency regulation, peak load avoidance) they are usually bidding on.
Traditionally water heaters were only on at night.
https://www.amazon.com/Cash-Acme-Thermostatic-Temperature-Ap...
That's a very low tech solution that could take some advantage, and thermal mass of water is pretty high, especially if the tank is well insulated.