I didn't hear the programme but given that it was likely to be linked to this in The Sun
https://www.thesun.co.uk/fabulous/7439926/who-cares-wins-health-awards-nominees/
the app would appear to be this one
https://goodsamapp.org/
Actually, having just typed that, I've now taken a look at the BBC website, which confirms that the show featured the "Who Cares Wins" awards, so I'm more confident than ever that it's the right app. If you still need confirmation you can listen to the show again here:
https://www.bbc.co.uk/radio/play/m0000p2v
(You don't need to listen to all of it; you can move the slider towards the end of the show).
As I see it, the aim of the app is to get a defibrillator (and a trained operator) to where it's needed as quicky as possible. If you ever get the chance to view the Department of Health's official training video about using defibrillators you'll see me showing you how it's done ;-)