Something like a thermostat or a smart fridge – have you seen any? If so, please share with a video or two.
Software defined radios are kinda a stretch. The radio hardware isn’t running Linux. There’s a receiver that converts the signal to digital and then a Linux computer processes the signal. Basically the exact same thing as my computer having a radio receiver plugged in to it but packaged up as a standalone thing. If that counts, my keyboard runs Linux.