The Linux kernel ("hijack") sits between the hardware and the closed-source "player" app. Hijack can only see the inputs and outputs, and modify those to a degree.

The "player" is what interprets and assigns "context/meaning" and "actions" to events like buttons (including the IR remote buttons).

So we have a bit of a limitation in what can happen there. I thought there was something already that would output the current "source" (FM/AM/AUX/MP3..) and similar info. Or at least the player would output a line for it whenever it changed.

But.. it's been a while.

If after looking more you don't find it, then perhaps I'll have a look too. I think we could have the current source ID just periodically dumped to the serial port if need be.