Maybe not exactly what you're looking for, but I recently learned about Traksy and Realtimetrains, which both give some interesting live information.
They look interesting. I'll try them out over the next few day.
https://www.opentraintimes.com/ Is quite detailed. Also good for checking how late your train was for Delay Repay purposes, especially as you can bookmark a particular service to refer back to later.
App wise I use Train Track by quatabyte on Android, Train Home by Thomas Thorpe on iOS.
Also realtimetrains.co.uk works well in a mobile browser though they no longer do an app.
I think you can bookmark services on all the sites mentioned here. Although, I suppose, some sites may delete the services once they've arrived.
Probably. I know that I've copied the OTT URL for the service's page into the notes field in a calendar entry before travelling, and it still works a couple of weeks later, although if I go back further it says "Schedule L15359 was not valid on 2024-03-19", so I'm guessing they get dumped after a month. Probably a limitation of the Network Rail data/licence.
I should have also mentioned Open Train Times. A bit more technical but the maps are useful for seeing where your train is, if it's delayed.
UK Rail and Trains
Talk about the UK rail network.