There’s an AED (Automated External Defibrillator) at Forest Hill station. It’s kept in the ticket office so you need to ask for it. They’ll let you take it away from the station in the event of an emergency nearby (as I discovered a couple of weeks ago. Fortunately didn’t need to use it.)
Are there any other accessible AED’s in the area? Do all Overground stations have one?
That map is incomplete. As far as I’m aware, almost all London Overground managed stations have one by now. New Cross Gate, Brockley, Honor Oak Park, Forest Hill, Sydenham and Crystal Palace have them.