One app that has been really useful over the winter months is Hugo.
This is an app that you install on a mobile device (Android or iOS) and with some simple setup questions and permissions granting, it links directly to your smart meter data*. In much the same way as the in-home display units do.

It then shows information on consumption from the previous day back to the point at which the smart meter was installed. This can be aggregated by week, month and year. It displays this in both kWh and £ which is very useful. Standing charges and VAT can be toggled for the cost data.

The bit that works for me is the budgeting page: You can set a tariff and a desired daily spend and the app will then tell you how you are doing in meeting that budget based on your consumption**. The app displays how much you may be over or under your daily/weekly/monthly/annual budget and has a helpful graph to show how you are doing against a projected and prorated annual budget.

Another function that I've not used because we went directly through our energy provider's app is the ability to sign up for energy savings sessions. These were trialled over the winter and involved customers ramping down energy consumption at times set by the National Grid. Customers then received a payment based on their energy savings. The Hugo app also gives users energy savings tips.

Finally, it is possible to buy a carbon offset for the imported electricity to your home, either for a year or a month. I've not used this, and need to look into what an offset entails (not all offsets are created equally!!) but I like that the option is there.

* to any conspiracy theorists reading this, no one can control your house, meter or mind by doing this.
** to any conspiracy theorists reading this, it doesn't turn off your electricity to make you hit a predefined budget.