Spot price (+margin) contracts became common in Finland at least some years ago. Most energy companies provide them now. The margin is something like 0.30–0.40 cent/kWh.

We buy energy from any Finnish seller with contract separate from transfer of electricity (a natural monopoly).

Yes, you just purchase your electricity with a market price contract (usually with added margin) and every day the next day prices are published around 3pm Finnish time (perhaps 12 UTC). Then just use the free APIs to load data and use the data to adjust when you spend electricity on what. E.g. to charge EV on cheapest hours, or load batteries, or when you fire up your electric Sauna...

These days the price is different for every hour, in near future they move to 1/4 hour pricing.

About 10% of finnish household contracts are market price contracts. Most of the contracts are kinda continuous (price changes every 12 months) or fixed (e.g. a two year fixed price contract).

This is also common in Denmark. You get the new estimated hour-by-hour rates around noon the day before.

I actually made a little calendar subscription service[1] to help our household plan when to run the dishwasher, drier etc. and we've saved about 50% this quarter despite the rising electricity costs. You can usually tell when it's cheap/almost free too just by sticking your head out the window, since it's mostly always the cheapest on especially windy days.

[1] https://el.simongray.dk/

It will depend on where you live, very common in Sweden with many companies offering it.