I expect TfL's "Tube departure boards, line status and station status"[0] feed would suffice. It's updated every 30 seconds. Plenty more data available too. [0

I expect TfL's "Tube departure boards, line status and station status"[0] feed would suffice. It's updated every 30 seconds. Plenty more data available too. [0]: https://tfl.gov.uk/info-for/open-data-users/ https://tfl.gov.uk/info-for/open-data-users/