To get the data out, you can just call their API to get daily consuption figures, split into half hourly blocks[0]. They also allow you to just download a CVS file directly from the energy use section of their website.
The data in the API is only update daily, but they can give you a tiny addon device[1] for free which will allow you to access live usage in realtime (updates ever 10 seconds I think).
I use a Home Assistant integration to collect all this data live there.
To make use of the smart meter, they also have a series of tarrifs which change price dynamically. The simplist is Tracker[2] which charges you a different price per unit every day based on the wholesale price. There's also Agile[3] which is the same concept but the price changes every 30 minutes with higher highs and lower lows. That one is great if you can shift your energy usage outside of peak times.
They also have "intelligent" tarrifs where you allow them to control your car charger[4] or home battery[5] so it charges when it's cheapest.
Octopus are doing really great things in the UK and part of their business is that they sell the backend as a service to other energy companies who were previously stuck in the stone age as Kraken[6].
[0] https://developer.octopus.energy/docs/api/
[1] https://octopus.energy/blog/octopus-home-mini/
[2] https://octopus.energy/smart/tracker/
[3] https://octopus.energy/smart/agile/
[4] https://octopus.energy/smart/intelligent-octopus-go/