I was rather taken by surprise by this, and haven't seen it mentioned, so I thought I'd point it out. At the bottom of the home screen of the BA App there is a set of example fares "Return Fares from London". This is actually a rather nice flight and fare finder tool.

Firstly if you go into the "show more", and hit the "change" icon, you have a lot of control over what you can look at. So you can look at day trip business class fares to Europe from London, scroll through the list, then click on the list to zero in on the best fares. It's quite similar to the "our cheapest fares" on the website, except considerably less clunky, and it gives actual fares you can book for each day of the month rather than averaged fares like "cheapest flights". Best of all the "back" button works (the web site doesn't really allow this), so it's really great for browsing back and forwards.

And then back on the home screen, there's another button to change the "from London" to your local airport. This is less comprehensive and for some airports such as Jersey gives you just London and Dublin as options, but I was able to browse Oslo to the US in J for example.

I don't think it replaces google flights or the matrix for serious hunting around, but it is really very usable for looking for odd trips here and there or ideas of places to go.